Why do people Piss and Moan?

You guys crack me up.
The range of responses is amazing, and I like certain ones more than some.

I liked,
"you married her"
"Stash the BMW"
"Be a man and stand toe to toe with her"

NOBODY said "quit yer pissin and moaning" which I expected.

It's not like she bitches all the time or anything thank God (I'da been gone so long ago nobody would remember what I even looked like.)

Been married for 28 years and raised four kids and we aren't going anywhere.
It just annoys me sometimes, when she doesn't seem to realize how bad off some people are these days.