TT is too good a hand to be limp/calling with and playing only for set value. We only hit like 1/8 times or something and we're DEFINITELY not stacking the guy everytime we do hit. I'm sure it's not -EV or anything to limp and play it for set value, but I think it's a ton more +EV to raise and build a pot so that at worst, you lose a c-bet when you're outflopped and you'll find it's a lot easier to stack your opponent in a raised pot than a limped one.

edit: It's the same reason I'm raising with 99 and usually 88 also. 77 and below and I'll start to entertain a limp because at that point, our hand will be tough to play when called and we have to play a flop OOP.