I hate it as much as the next person, but I'll suck it up as long as they didn't pee on the seat.

The urine does not annoy me, but leftover s#it does!

I am on a septic tank and I still flush each time I go.  I have heard that people do it to conserve water, to keep the septic tank low, or that the sound wakes someone else up in the middle of the night.  Personally, I would rather hear the toilet flush and have an empty toilet in the morning than to wake up to sewage smells coming from the bathroom!

My friend's mom and sister would not flush after urinating in their home.  They had a septic tank, and I guess that had something to do with it.  It's a bit gross.  At least they kept it to the confines of their own home, though.