What is the point of ID cards?

ID cards seem to be a constant desire of authortarian governments around the world. What exactly is the point of them?

It seems to me that they acheive very little for well meaning governments, but are disasterous in the hands of tyrants.

Criminals don't play by the rules, so they either avoid systems that require ID cards, find loopholes to exploit or even use the systems to commit crime themselves. In the end these systems only ever end up making normal, law abiding people's lives more difficult, at massive expense to the taxpayer.

If you believe in freedom, then you have to be against these tools of tyranny.