Because there is a verse in the quran which Allah says (I'm paraphrasing) the men are allowed to marry up to 4 wives. However if a man is not able to do it correctly, then it is better for him to only have 1 wife. Don't let certain people and their mislam (misunderstood concept Islam) confuse you.

"I don't think so. Homey don't play dat."
Homey Da Clown