The Kosher laws, as I understand it, were written as a way to make sure the Law was kept to the fullest degree. Like many other Pharisaic traditions, they had good intentions but became overly burdensome, and they ended up adding to God's commands.

It's not unlike some churches writing "rules" designed to keep us out of trouble, but which also tend to become "laws unto themselves." For example:

Christians don't dance.
Christians don't use playing cards.
Christians completely abstain from alcohol.
Christians don't wear makeup and their shirts must have collars.

You get the idea. The Scriptures make no such demands on us, but many church traditions - just like the Pharisaical laws - impose requirements like these to "help make sure" that we don't lust, envy, get drunk, cause another to stumble, etc.

(Acts 4:19, 5:29, 2 Cor. 1:24, Matt. 15:9)

-Robin