It's mainly because I rarely think about it. I never developed the habit. My parents didn't stress that stuff and were long gone by the time it mattered so I taught myself all of this stuff. They didn't instill a brushing teeth habit in me either but I eventually picked one up because I knew I'd ruin my teeth if I didn't. Even then I know I don't brush as often as most people. If I do it three times in a day it's rare.
I'm not going to argue that it's a good way of living just that I've been doing it going on 30 years now and I seriously doubt if it has ever gotten me sick. It isn't like I'm taking my food, spreading poop on it, and eating it. Plus, I wash my hands before meals anyway. How often are you people going to the bathroom and how much paper are you using? I only go once or twice a day now that I'm not constantly in w/d from opioids and I use almost enough paper to clog the toilet every time. There are at least 4-5 layers of it between my fingers and my asshole. I buy the good stuff too, toilet paper is something I'd never skimp on my asshole requires the most fluffy/soft/triple-ply stuff on the market. I don't understand how some people in this thread are smelling poop on themselves after going. I can honestly say that I've never had that problem.
Also your toilet is spreading poo everywhere everytime you flush it even if the lid is on it. Your toothbrush probably has more of your own poop on it than your hand after wiping. People touch their assholes more often than just going too. Everyone is guilty of picking out their underwear or having an itch and digging in there to relieve it from time to time.
Like I said I'm more worried about touching other peoples hands than I am any part of my own body. But if I washed my hands every time I touched someone else I'd never get anything done. Besides, I'm squeaky clean when I plan on being around other people anyway. Why should they care what I'm doing in my own bathroom? At least I'm not turning on the water and pretending like I know _alot_ of people do.