Ok here's the thing...
with ANY pocket pair you have a 1 in 8.5 chance of hitting trips on the flop. If nobody has preflop raised and you are in late position limp to see the flop. If you don't hit trips then you have to assess where you are at. This game is more than just about the cards. Any hand you are in could be worth a bluff if the situation is right. With a pocket pair, even if your bluff is called, you still do have a couple of outs... Also, keep in mind that if you flop the set, you don't have to worry TOO hard about straight and flush draws. Even if they hit, you still have a lot of outs to improve to a boat.
Give me a set of 2's every hand and let me play against straight and flush draws. I will take their stacks.
Just to add to this, yes a set of 2's isn't as sexy as say a set of aces. You can still be beat by 2 pair that boats up when you boat up. You could lose to a higher set. Whatever. A set is a set and odds
are pretty good you are way ahead on the flop.