Because we've had to use their bathroom while I finish grouting the tile in mine.

My obnoxious 15 year old child is pouting over having to completely hose down his bathroom because it's infested with a greasy layer of his filth.

Guess what little man...I've been cleaning bathrooms years before I reached your mature age and YOU do not get to tell me how it's done. That's 25-27 years of experience with a can of cleanser and my head in a toilet that you don't have.

If I say it's disgusting in there, it's disgusting in there, and you can spend an hour of your precious media laden time to dazzle me with how non-urine-y it can smell like.

Bonus, maybe, just maybe, the your fingernails might become clean in the process.