See, when I was a lass, there were lots and lots of products for greesy hair. This was an issue that lots of people have. Then some point in the late 80s, it seems like large swaths of the population solved their 'problem hair' by washing it more than once/twice a week and wow, that whole area of hair problem just dissappeared!
I think it's perfectly fine not to shower every day if you do a good strip wash in the sink on the other days, but doing a good strip wash takes longer and generally involves slooshing water all over the place, showers are quicker and contained. Not washing at all for some days is grim. You might not be able to smell yourself, you might be used to your DH's smell, but you won't be clean. It's OK not to be clean if you're a grown up and don't want to be, just don't sit next to me on the train, thanks.
OP - I can see that it would annoy you because it does seem disrespectful. It's like he doesn't care that you would prefer him to be clean, he doesn't care about being sexually attractive to you. It would doubly annoy me if he'd shower and clean himself before going out, so showing he was prepared to make an effort for other people but not you. (DH showers at least once, usually twice a day, but then he does a lot of sport/exercise, I shower daily, sometimes twice as well if I've done exercise, but I do a lot less than DH so that's a rarer thing to happen)