My roommate only washes up if he poops, never after peeing. Now every time I’m in any of the common areas I have to wash my hands after touching anything I haven’t wiped down. Thus, I wash my hands twice every time I use the bathroom; once as normal and again in the kitchen because I touched the taps, light switch and door handle in the bathroom which likely have groin sweat on them… /rant
A lot of people wipe their butt, flush the toilet, wqsh their hands, dry them, and leave the toilet.
This means that at least the toilet flushing button is often very dirty with poo germs. Depending on how you two and people visiting you handle the flushing, ut might make sense to always wash hands after flushing the toilet.
Otherwise… Whatever.