I've experienced it at different times in different environments, it's not always overt either.
When I was 18 I worked in a local pub, it didn't allow women in the bar area but no issues with them working behind the bar. If I needed to work at a low level, e.g., refilling fridges or cleaning shelves, there would always be some bright spark who would quip "while you're down there, love..."
Worked in training in my 20s, incredibly good at my job and attached to a specialist team only answerable to senior management. My role involved reviewing random samples of case files to identify any trends that indicated training needs as well as creating training packages to address those needs, I would also write guidance for staff on new processes, etc. So many times I'd be condescended to by male managers from other teams/departments about this training package or that piece of guidance. Commonly, they'd stop me mid-delivery to quibble over some point or other and try make on that I didn't understand the new guidance. A very blunt "I wrote it" usually stopped the worst of it but some would take that as further challenge to try take me down a notch.
The male manager twice my age who thought it appropriate to buy me a vibrator and edible underwear in the Secret Santa.
The man behind the counter at a garage I went in regularly who, when my first pregnancy started blatantly showing, asked if I was pregnant. When I said yes, he gestured at my body and said "well that's this ruined".
A locksmith that I had to call out after snapping my key in the lock who felt the need to tell me "you've got cracking tits, if you don't mind me saying". Very quickly shut up when DH came strolling up the road back from the shop and he realised I wasn't on my own.
Right months pregnant, walking home with my shopping. White van pulls up at the traffic lights as I was crossing and the two men inside shouted "oy oy, fatty boom boom!" before mooing at me and driving off laughing.
Driving instructor who told me I was going to need more lessons because I'm a woman and woman are slower to learn. Told me to pretend I was shopping and that there were handbags and shoes in the mirrors so I'd remember to look at them because that's all women like to do.
It's not all men but it is almost always a man and when these things happen they always have a horrible undertone of dominance, superiority, control, aggression, or are sexual (or all five). I think for a lot of men, there is a very thin veneer of civility over the top of their true nature and they view women as easy targets for letting that nature show.