You probably need to find out why jews don't eat pork, as the islam(same for christianity) is heavily influenced by judaism. Early christians didn't eat pork as well.
Because Jews, Christians, and Muslims all follow the God of Abraham. It is in the Old Testament. Only reason Christians say you can now eat because of the New Testament, which the Muslims and Jews don't believe in.
Leviticus 11:3 - Whatsoever parteth the hoof, and is clovenfooted, and cheweth the cud, among the beasts, that shall ye eat.
Pigs don't chew their cud.
Read Acts 10 to understand why Christians say it is okay. That's on Peter's vision, but there is also another verse concerning burnt offerings that is also used, but I don't have time to find it.