Why is it that most religions seem to involve serving something?

Christianity, Islam and Judaism all involve serving God. Buddhism and Taoism can be seen to involve serving the greater good of humanity (although I'm sure some would disagree). Things like Hinduism involve serving the Gods or Gods that an individual worships. There are many other examples of religions that involve servitude of some sort or another.

The only religion I can think of off the top of my head that does not involve any servitude at all is satanism, but that's not really even a religion, more of a philosophy.

I think it's because humans have a natural herd instinct, a natural desire to fall in line and serve something greater than themselves. What do you think?

EDIT: Forgot to make 'God' starting with a capital letter.

[This message has been edited by panthermodern (edited 12-19-2006).]