I tried the excellent random subsector generator over at The Zhodani Base. I took a look at the world stats and discovered a couple things I could not help but pick at. First I decided to pick the worlds that were the movers and shakers across the subsector. For that I highlighted the four P's: 'Port, Politics, Populations, Propulsion.
Port is starport. If it isn't an 'A' then new starships are not produced for commercial use though the military can build some. the planet does not wield a lot of economic power.
Polity is the world government. I'm pretty liberal here and only a result of '7' Balkanization makes me think people might not be looking at other worlds but their neighbors.
Population has to be at least in the millions to build an appreciable number of merchant ships.
Propulsion is actually Tech Level. If you don't rate at least a 9 you haven't got the ability to build jump drives.
So if a world has a TL of at least 9 and a population of several millions why the futz wouldn't they build a class A starport?
Strangely enough my subsector so far has two movers and shakers. One has a population of 300 million, an A starport, and a TL of 11. The other has a population of 10 billion, a TL of 12 but a B starport.
Reasons to not build starships may be:
The planet has a severe shortage of a mineral required to build jump drives.
The planet has a xenophobic culture and does not desire offworld contact.
The planet lacks the specialized knowledge to build ftl rives but is otherwise at the Tl to do so.
The planet can buy starships cheaper offworld.
The planet is prevented from building starships or spacecraft by treaty imposed on it. If you just kicked your rival's teeth in you may not want to occupy their whole planet but you will want them to stay in their own back yard.
However this paucity of starports deserves a story arc/campaign seed. For this I turn to the megacorporations. In the past on Earth huge corporations like the British East India Company grew huger still by controlling commodities. they had their fingers in everything from silks to opium. In an interstellar economy this becomes more difficult. A world could probably handle all its needs with the resources on hand especially if you threw in a few moons and a planetoid belt. Yes you could ship stuff to them that you made more cheaply elsewhere but that sort of quarter credit a kilo profit doesn't make you the peer of the sector governor.
After the commodities corporations fell out of fashion the new business model provided ways to use time and ideas more profitably. The railroads and steamship companies made travel and shipping faster and more profitable. Companies also became innovators. they produced all manner of appliances and devices to make your life and business better. they also invented advertising to convince you their crap would make your life better.
That's harder in Traveller though. travel is about as fast as it is going to get. You aren't going to build a jump drive to get to your destination in five days for example and usually the higher jump numbers are reserved for the military and so fuel hungry it's hard to haul useful cargo. Ditto for insystem travel. When you're only going a from the jump limit to the high port even 6 gees isn't going to matter that much.
Innovations becomes a thorny issue. If you assume 3D printing you can build whatever the heck you want on at TL 8 or higher. A company could license designs for the printers, license the printers and go through more copyright infringement suits than Disney Corp. did over those pogs back in the 90's. But people are going to hack and steal your designs regardless. People are going to refill your material cartridges they are supposed to replace and when some genius figures out a way to print another 3D printer it all falls apart, not to mention leading to Von Neumann machines that ALWAYS revolt. Also you need more narcs and police to enforce your copyrights and patents than the Emperor had stormtroopers. All that eats profit.
What's left to monopolize, monetize and run into the ground?
New worlds! New worlds provide living space but may need terraforming or genetically altered colonists to occupy. Both of those are huge long term projects for big bloated companies. But new worlds also contain new commodities. Unique organic compounds for one thing that take the form of pharmaceuticals, luxury items, new food staples (or dietary supplements of they aren't nutritious), pets/slaves/servants. You can't three D a sun diamond from the desert world of Zaranal after all.
To control these items you control the spaceways and trade. Difficult, not impossible. First you start starship manufacture. You build the ships, you standardize everything between the models you build. If there's any competition you sell at a loss long enough to make them go under. Moreover if there are any rare substances you need for ftl or maneuver drives you buy those up before the little guys can.
Open a bank. Give loans on the ships you sell and make sure the new owners will be hauling cargo to make their mortgage payments. Offer discounts on the standard designs you crank out but in the end starve them so they can't take a chance on hopping off the beaten trail to make discoveries that might be nonexistent, unprofitable or deadly.
Open subsidized merchant runs to various planets making it cheaper for them to use your line than build their own ships. For that matter build warships so that the local governments don't have to and won't need their own spaceports.
You also need some pull with the government but by the time you've bankrupted a few worlds' space programs you're big enough to eat with the big dogs. get some influence over the Scouts and making discoveries is their job. Demand regular mail services, surveys of hazards in known systems and worlds, anything that keeps them on the settled side of the frontier.
Finally send your own merchant cruisers out to make the discoveries, perform first contact, and bring in the goods. Your exploitation errr exploration has to be far more organized and widespread than anything a dinky free trader can put up. Make sure you have labs and research personnel to analyze everything. Those eight legged rats' droppings may be the best anagathic component ever found. Of course you're also going to buy any samples from free traders you analyze that turn out to be profitable.
Between ship building, banking, pharmaceuticals, mining related services you should be ready to become a megacorporation. If the sector governor has to make an appointment to see you you're on the right track. Keep him waiting or reschedule.