an article on Kosher
http://www.jewfaq.org/kashrut.htmHowever, health is not the only reason for Jewish dietary laws. Many of the laws of kashrut have no known connection with health. To the best of our modern scientific knowledge, there is no reason why camel or rabbit meat (both treif) is any less healthy than cow or goat meat. In addition, some of the health benefits to be derived from kashrut were not made obsolete by the refrigerator. For example, there is some evidence that eating meat and dairy together interferes with digestion, and no modern food preparation technique reproduces the health benefit of the kosher law of eating them separately.
In recent years, several secular sources that have seriously looked into this matter have acknowledged that health does not explain these prohibitions. Some have suggested that the prohibitions are instead derived from environmental considerations. For example, a camel (which is not kosher) is more useful as a beast of burden than as a source of food. In the Middle Eastern climate, the pig consumes a quantity of food that is disproportional to its value as a food source. But again, these are not reasons that come from Jewish tradition.
The short answer to why Jews observe these laws is: because the Torah says so. The Torah does not specify any reason for these laws, and for a Torah-observant, traditional Jew, there is no need for any other reason. Some have suggested that the laws of kashrut fall into the category of "chukkim," laws for which there is no reason. We show our obedience to G-d by following these laws even though we do not know the reason. Others, however, have tried to ascertain G-d's reason for imposing these laws. I think if a person does not, or does eat something, to give glory to God, then in that intent and purpose they do give glory to God.