As you said, by raising you make some people fold. You don't want to go post-flop with too many players involved, cause the more person there is, the more chances there is than someone hit the board.
By raising, only people with good or correct hands will call you, reducing the chance of someone else than you hitting the board. Of course, after that you need to play well to take advantage of that, but it should be easier and more profitable.
You say you're trying to make more money by getting more persons involved, but limping (calling the BB), isn't much money, and if they have bad hands they will either fold post flop or hit the board and screw you with a weaker hand. So by raising, you increase both your chances and the money in the pot.
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