I don't know either. Some people, well, many people are truly just above retards
You want a better WTF story. The jackass that owned my rental house before me built a nice tile surround in the shower. I come to find out after a couple years of owning the place that he attached all the tile to DRYWALL!! Not even greenboard, just ordinary Sheetrock. Needless to say that mold exploded as the wet Sheetrock started to get crumbly.
I had to tear everything out, replace the studs that were also moldy, run an ozone generator and refinish everything.
WTF people. If you don't know, then just ask someone.