Kyle W. wrote:
Why is it, toothpaste clings to the inside of my drains?

It's not like anyone brushes their teeth, without "wasting" water.
The drains begin to drain slow, then end up stinking.

I was talking to some neighbors, they say they have the same problem.

The drains are nasty, this is pvc pipe. I've cleaned them before, the
stench is overwhelming.

Some boiling water with a little dish detergent, poured into the drain,
should clean it fairly well. Follow with a little full-strength bleach.
Take out the plug, remove remaining hair, etc. Ick! Hate doing it.