我看主要还是和人自己有关。有谁会在热闹的大街上方便呢？^_^

应该与缺少厕所有关吧？

另外，“DO NOT PEE HERE！We pee back.”

指的是一种能反射小便的墙，高科技啊：

https://www.entrepreneur.com/article/249023

San Francisco’s Department of Public Works is combatting the disgusting problem of tinkling in public with a completely off-the-wall solution -- walls that “pee” back on the jerks who pee on them.