I shower every morning without fail. In summer or on days when I have done something to get sweaty or dirty, I will have a shower at night too. I get missing the odd day in winter if you're not going anywhere but not showering daily is so gross to me. I would have thought it's just basic personal hygiene along with brushing teeth twice per day, wearing clean underwear etc.
I have a couple of friends who don't shower daily and you can tell. They smell at times, there is a definite odour. They don't look fresh. I'm sure they also think they don't smell and no one notices...let me tell you, other people definitely do..
There is no way I would sleep beside anyone who went days without showering - yuck! How grotty must the bed get!