This is one of those things that probably didn’t exist 10 years ago. Before ubiquitous social networking you either washed your bike with a hose, some water bottles or just didn’t bother. Now, it’s all about putting your bike in the shower? Extra likes if it’s a hotel shower and during a race weekend.
I’ve done this once and it’s both a gigantic waste of time and gigantic mess. I’m not quite sure what the benefit is? Trying to clean the bike with the shower head doesn’t work very well, water gets everywhere and the kind of grime that comes off a bike very easily stains the materials modern tubs are made of.