As with most classless games Traveller characters are very strongly identified with their skills. In fact it's often more stronger than most games. You have t make hard decisions about what service to enter to get the sort of skills you want. You may ache to be a hot shot pilot but with a low social standing the Navy is out. A low endurance will preclude the Scouts (if you want to live). So farm boy winds up flying a free trader instead of a Rampart starfighter. Add to this you are constantly balancing your quest for skills against aging and survival.
In many versions of Traveller increasing skills is a very long, expensive and uncertain process.
Naturally no one in Traveller ever thinks they have enough skills or levels in skills. People didn't think it when they generated their characters in Classic Traveller. Little has changed that mindset. When we got a look at Mercenary, wow! Suddenly you could go for advanced character generation with the possibility of a skill gained for every year of a term! That made Scouts look like pikers in the basic system. Moar skilz was popular with some people. Others pointed out you now had to roll for survival every year and that your spelling was abominable. Me, I longed for an advanced character generation system for Belters and Barbarians. All this led to the phenomenon known as skill bloat in later years and later editions. Without giving out more skills we have several ways of closing the skills deficit.
My favorite way is pretty simple. Make sure your adventures give everyone something to do. Look over their skills and tailor challenges and events to suit them if you can. Note this doesn't mean every adventure has an Iron Chef competition to showcase your Steward's fancy grilled cheese sandwich merely that everyone has something to do.
I'm a big fan of 0-Level skills. Most characters have 0-Level in weapons (this comes from possessing the adventurer gene.) A 0-Level skill allows you to perform routine tasks without negative DMs or killing yourself outright. Characters should be encouraged to use 0-Level skills and please note I qualified kill with 'outright'. A related technique would be to give a character a lower level in a related skill. In Classic Traveller Pilot functions as Ship's Boat at one level lower for example.
Advanced character generation is the official method I suppose. While it does lead to a lot of skills and levels in skills many of them have a narrow application. A merc helping explore a derelict ship won't have a lot of call for Forward Obs-3. You might be better off bringing the Steward bearing lunch (grilled cheese with Kudie bacon anyone?) Similarly merchant princes do not belong in a fire fight although being able to build a fort out of cargo containers might save lives. So even with Advanced character generation you'd still have to make sure people have things to do.
In a campaign that concentrates on free traders or a mercenary unit all the characters are merchants or ground pounders everyone has similar characters and scenarios all have a common basis. You're trying to make the deal of the week or honor your latest ticket.