bakho:
Yeah, you're right. They're not really premade characters, just defined concepts.
What do you mean by "concepts"? Like, battlefield controller, healer, tank, damage dealer... or like Wizard, Warrior, Wastrel... or like "Naive Farmbot', 'Pragmatic Princeling', 'Underhanded Smuckler'?
Because the first lets you manage group 'combat expectations', the second gives you a loose idea of future battlefield/social encounter expectations but gives the Players more control, and the last one takes an awful lot of "roleplaying possibility" out of the Player's hands.
All three are fine by me as a Player, but you'll get very different results depending on what you mean.
And as noted, even Completely Premade Characters will get you people who will show up to play, just ignore all the "Don't you trust your Players?" questions. Because if you do go the Completely Premade route, no, clearly you don't trust the Players to make what you need for the campaign. If they don't like it (and many won't) there are plenty of games out there for them and still plenty of Players for you (just the Completely Premade route does have less enthusiasts, so instead turnign away droves once you've filled the roster, you might only turn away a few people).