Not to mention many skills can be used even with no skill level at no penalty - you just didn't get a bonus.
That also exists in MgT (skills that have no untrained penalty), and it's (IMHO) different from level 0 (though in this case level 0 have little sense, if any).
My point is that CT uses them in a wide variation of ways. Sometimes no Stat is referenced for a task. Sometimes the entire stat is referenced (as with throwing a blade--entire DEX used as a DM). Sometimes, a certain level of stat gets you a certain bonus.
IMO, this is much better than one-size-fits all bonuses where +1 to EDU increases every task that EDU governs.
AFAIK this happens in all versions of Traveller...
This said, in CT the stats modifiers used not to be progressive, but usually more than +1 if you reached a treeshold, being 0 if lower tan it, or negative modifiers (also usually more than -1) if they were too low. Personaly, I prefeer a more progresive stats DMs (and in this way T4/T5 achieve it better).
Also remember that a +1 modifier is significant in 2d6, while quite less so when you roll more dice (lesser significant the more dice you roll).
As for Skill-0 in CT, I think it was used A LOT.
First off, all of the careers in Book 1 provided a Level-0 skill for every weapon in that book. That's a lot of skills right there.
Defaults skills, like Air/Raft, ATV, Forward Observer, Steward, and Vacc Suit are encouraged as free Level-0 skills, if the Ref thinks it appropriate for the character.
That's a decent amount of skills.
While CT (LBB1, pg 22) talked about level 0 skills, no rules were given for them, being enterily at referee's discrection. So you could not attain steward 0, yet it could be given to you by the referee, if he/she felt it adequate.
Personally, when I refereed CT/MT, I assumed every character to have all the skills listed in his service (for basic CharGen) or MOS (for advanced Chargen) tables as level 0 (unless they had them higher, off course). Imagine my surprise when I say MgT doing exactly this same thing...