If you have good role models perhaps it's hard to understand but some of us grew up with very few positive male role models. My idea of what men are like was based on teenage boys at school (mostly awful), my dad (he's OK but I didn't see him very much and I don't think I ever really saw him doing housework), some of my mum's friends (only ever saw snapshots; adult men don't usually befriend teenage children of their friends), my uncle (violent and abusive), my grandad (old fashioned, sexist, though he did take over cooking and cleaning when my grandma got ill).
My mum had been in loads of abusive relationships so only had horror stories about men, which I took for granted (and honestly, I think so did she. I don't think she has high expectations of men. She is constantly amazed if I say anything about what DH is like.)
Society gave me the message: Men are useless/lazy with housework and have to be nagged constantly. Men are hopeless with babies/children. In fact they don't really even want babies or children, like women do. Men are emotionally stunted, and deal with emotions via aggression. Men don't understand or empathise with women. Men find fart jokes funny and like sport and gaming and star wars and superheroes, they definitely don't like the things you like, so you'll never have common interests. Men are constantly gagging for/obsessed with sex and "need" it, very visual, any time they see women it makes them want sex, it's unfair to tease them, OTOH you can use this to manipulate them, it's basically your only advantage so might as well use it. So empowerfulising!!!
I really had this impression that men are basically an entirely different, mysterious species, that you have to relate to in a wholly different way to how you relate to women, and they were basically all a bit shit so it was unfortunate because if you were attracted to men you had to put up with a load of crap in order to get the good parts of a relationship. Weirdly I did actually know I was attracted to women as a teenager but hardly anyone my age was out back then, so I didn't really consider dating girls as a realistic possibility.
My mum also used to rave about books like "Men are from Mars" which did not entirely dispel the myth.
Because I had such a low bar for men in general I tended to think if I met someone who was tidy, OR who wasn't constantly burping/farting/obsessed with sport, OR who showed a genuine interest in having children (etc) that this was some kind of special rare unicorn, the idea of looking for all of these things in one man just never even occurred to me that it was possible, it didn't compute.
Also, first teenage boyfriends, you don't think about housework etc at that age. And I was fairly messy and lazy at that age too so it was actually fairly likely that most boys were tidier than me 
But also I have observed that a lot of people in general, when they are young they throw their clothes on the floor and they go out drinking and they eat crap and they smoke and they have unproductive hobbies and they might take drugs on occasion etc. But I can't think of a single female friend who has stuck to this past about their mid twenties. They settle down, they get more grown up. I think that because women often do this we sort of assume that men will do this too - but they don't seem to do it in the same way. I do know men who went from the loud, lazy, laddish type to a decent, kind, grown up adult - but the vast vast majority, they either don't do this at all and stick with the student type habits all their life, or they change in response to a female partner because she doesn't put up with it. Or they were never like that at all in the first place.
In fact this is going to sound absolutely neanderthal but I think National Service really fulfilled this role well for a lot of men of my grandad's generation. Having that experience of the army discipline really instilled in them a sense of morality about laziness, cleanliness, tidiness, manners etc.