I discussed Classic Traveller (CT) skills before, and I'll discuss them here again, in greater detail, this time about their nature. A common misconception is that skills in CT work like skills in a D20 game, or Mongoose Traveller (MGT) for that matter - that is, as modifiers to the task roll (2d6 for 8+ in MGT). This indeed is the case of weapon skills in combat - they add the skill as modifier to the combat roll, but also (in the case of melee weapons, that is) as a penalty to attack the character. But many other skills are not meant to serve as modifiers in some standardized task system; a lot of them are actually "all-or-nothing" character features.
Let's see: Bribery directly affects Reaction rolls, not "task" rolls; Engineering adds +2 per skill level to rolls to repair ship systems; Forgery applies a -2 DM per level to the throw to detect a forgery; Forward Observer actually applies a +4 DM to-hit by artillery fire per level; J-o-T simply gives you (regardless of level) Skill-0 in all skills; Leader allows you various command abilities per level; Medical-1 can give first aid and work as a medic aboard a starship, Medical-2 gives you a +DM to revive low passengers, Medical-3 makes you a real Doctor and Medical-3 plus DEX 8+ makes you a surgeon; a level in Navigation, Steward, Medic, Pilot or Engineering makes you employable as a starship crewman; Pilot gives you Ship's Boat at one level lower; and Vacc Suit-1 confers battledress/combat armor proficiency.
In short, these skills are somewhere between simple "+DM" skills ala MGT - and "Feats" (in D20) or "Proficiencies"(in ACKS) which actually give you a benefit above and beyond adding the skill level to rolls. Also, not all work the same way, some add a higher DM per skill level, and penalty for no skill varies from skill to skill.
MGT (as MegaTraveller did decades before that) "flattens" this "edginess" of CT, making it easier to run and remember - but losing some of the flavor and uniqueness on the way.