JJ, fishy game...do I want callers or don't I?

[zoobird]

It seems like I've read many times that with a hand like JJ I should be hoping that my pre-flop raise gets me heads up with one caller. My question is: in a fishy game, why? If people are calling me with weaker hands (A9, KJ, 54s), why isn't it a case of 'the more, the merrier'? I ran all sorts of scenarios on Poker Stove, and it seemed like with any reasonable range of hands for a loose game, the more callers I get the better. Am I missing something?