Q. ...why should people have to clean up cat crap and cat piss from someone else's cat?

A. Because it's there. Like cleaning up- after pigeons. Part of the rich tapestry of life.

Absolute bullshit. And self-serving bullshit at that. Its inconsiderate and irresponsible.

If you cause someone else's property to be despoiled, that's criminal mischief & should be actionable.