Why don't Jews eat pork?

The Torah forbids it for Jews.

In order to be kosher, food has to be prepared according to the kosher-laws (see Deuteronomy ch.14). These are explained in detail in the Talmud-volume of Chullin.
* Meat must be from those land animals which have split hooves and chew their cud (such as beef, venison and mutton).
* Fish have to have scales and fins. Shellfish are not kosher.
* Birds cannot be among those listed as forbidden in the Torah (Deuteronomy ch.14) and cannot be hunters/scavengers. In actual practice, today we eat only those species concerning which we have a tradition that they're permitted, such as domestic chicken, geese, pigeons and turkey.

* Animals must be slaughtered in the manner specified by Jewish law and must be free of all disease. In actual practice, those who keep kosher purchase meat which is certified as having been prepared in the kosher manner.
* As much blood as possible must be removed from meat before cooking, since consumption of blood is forbidden (Leviticus ch.17). This is done at home or by the kosher butcher, through salting, soaking and rinsing.

* Dairy and meat cannot be combined in the same meal and there's a waiting period between eating one and then the other. After dairy: 1/2 hour. After meat: 6 hours for most Jewish communities.

* Fruits and vegetables should be checked to be sure they're free of bugs. Some Jews avoid cauliflower, asparagus, and the like, because of the difficulty in checking them.

Additionally, food must be prepared and handled following kashrut-laws and with kosher ingredients only. Processed foods should be labeled as having had kosher supervision during their processing. Any food that does not meet these requirements cannot be eaten by those who are religiously observant Jews.

See also:

Could you give me a list of kosher and non-kosher types of fish?

Why do some Jews not keep kosher?

The use of rennet

The meat from pigs is not to be eaten by Jews, under the requirements of the Torah. It is listed as one of the unkosher animals. The reason for this is that the Torah specifies that animals to be eaten by Israelites must chew their cud and have split hooves. Pigs don't chew their cud, so therefore they're not a kosher species. Carnivores are not kosher; and neither are pigs, camels, rabbits or many other animals.

Leviticus 11:7: "And the swine, because it has a split hoof, and is cloven-footed, but does not chew the cud, it is unkosher for you."

Some less-religious Jews do eat pork, however. Only those who keep Kosher do not eat pork.

Answer 2

Judaism forbids the eating of any meat from a pig (pork, ham, bacon, etc.) because pigs are thought to be unclean animals; this is apparently based on the indiscriminate eating habits of pigs.

[Note: The above remarks are a common misconception held by non-Jews regarding Jewish dietary law. Below is a detailed explanation made by another poster that clearly explains how pigs are neither considered 'unclean' nor are they the only animal to be considered unfit for consumption according to kashrut (Jewish dietary laws.)

There's no basis in Judaism for the impression that "pigs are thought to be unclean animals."

Leviticus 11 and Deuteronomy 14 .state that the creatures forbidden to the Jews as food include the camel, rabbit, horse, pig, rodents, shellfish, twenty species of birds, almost all insects, and any animal that was injured, even if it's from a nominally kosher species.

The reason for these prohibitions is clearly stated in the Biblical text: Because you are children and holy people to your God. Avoid eating these creatures in order to remain holy.