Metro, don't forget that sims 3 haves a very bad error handling system, when a sim gets corrupted, instead of fixing the issue or removing the sim, the game ignores the error and the corruption spreads across all sims on the neighborhood: appearances are lost, family lines are screwed, sims start mass-missing school/work as schedules are lost, and then the game goes down in a giant ball of fire.
WA is rather guilty of this, traveling haves a high chance of damaging the data of one of your sims.
On the other hand with the correct CC, sim corruption is caught and dealt with on the spot, data isn't lost during travel nor your sim would get mysteriously married and with a random kid. There's a whole lot of other bugs in sims 3: some are errors not being caught and dealt with spreading the damage, some are design errors or small oversights like the food spoiling, others are things made through inefficient methods that end up slowing the game. To have a mostly bug-free experience, it seems the way of doing things is to use CC.
As for ea sending a message not to use CC and that they don't support it, it's common amongst game companies, as providing tech support to CC-using games is simply not possible and far beyond their scope. Which i wouldn't mind except for the fact that their tech support is horrible and i've gotten better results asking my questions in CC sites.
