I always thought it might be a good thing to raise low PP here because; it increases chances that the hands you are playing against are likley to pay you off when your set hits, you have the image of a strong hand allowing you to take more pots down with cbets (flop/action dependant of course), it starts building a good size pot early on making it easier to get it in if you want, and (even though I know most micros do not pay attention, yada yada) if they see you do this once with 33 they are more likley to call when you do it with AA in the same position.

Just my opinion....could be way off.