Does he sweat regularly? Play sports? If not, in the winter, shower twice per week. Doing otherwise is really falling into one of the weirdest forms of American prissiness.
In general I shower when my wife tells me I need to. On average that means every 2-3 days. How strange and wasteful would it be if someone washed their car every single morning regardless of whether it was dirty or had even been moved from the garage that day! (I work from home so the analogy frequently works)
I know he's making a broader point about risk but if you want to get over some crazy warped American perceptions to improve your life and the world, obsessive showering is as good a one as getting over delusions of risk of terrorist attacks.
Yeah, if by "massively" you mean he'll only be expected to have a possibly-fatal fall twice instead of five times.
Your post is extremely ignorant. It not only offensively and incorrectly ascribes daily showering to "prissiness" and "obsessiveness" (as if that's the reason I shower every day, instead of, you know, wanting to smell nice, look nice, and feel refreshed), it also claims that this is an American phenomenon (I'm Canadian, and many/most people I know shower daily. The ones I know who don't, smell). It also assumes all people are the same. Personally, I'd feel pretty sorry for your wife if you smell like I do after not showering that morning.
It's no more "bizarre" than the Japanese are bizarre for using those funky toilets with built-in bidets. Cultures may be different. Let them be different without judging, and without projecting.
I'm not here to judge you or your lifestyle, but if I were to rely on my significant other to tell me when I needed to shower, I would feel as though I was taking advantage of their good will. I want to take care of myself and be attractive for them, not use them as a smell-o-metre.