The Jewish and Islam religions do not eat pork because of their religious beliefs. Both of these religions observe the dietary laws that are indicated in the Hebrew Bible and Quran, respectively.
The Bible also restricts Christians from eating pork, but many people do not observe this law. Among the Christians, the Seventh-Adventist Church do not eat pork. According to Torah laws in the Hebrew Bible, a person may eat any animal that chew cud and has cloven hooves. A pig does not meet this qualities, thus Jews don't eat pork. The same reason is also given in the Islam religion.