The truth is that we can see their bad behaviour even before we have children. My lazy arse of an ex husband (he worked hard to earn money and was an incredibly lazy sod when it came to parenting and household management) was, in fact, lazy when I was dating him.
The difference is, it's far easier to ignore and tolerate that when you don't have kids. They don't change, it's just that having to give him a nudge every day to do the dishes when its his turn or take the bin out isn't a big deal when you're not knee deep in the domestic battlefield.
Additionally, I wasn't as fussed if the grout round the bath got mouldy when I was young and stupid, we were having fun, who cared?
So, no, they very rarely suddenly change, although they might indeed get even lazier when the kids come along, or more selfish very very few men suddenly turn from engaged, hard working in the home, fair and equitable partners to life sucking sods.
Men don't go from fully engaged and fair in the partnership to a complete arsehole once the kids come. The signs are there, we just don't realise how soul destroying the extra labour he causes and how much his unkind, unfair and irresponsible behaviour will be once kids come along.
I was young, stupid and had been raised to tolerate male lazy entitled selfishness. I did argue with my mum, but it still worms its way into your brain when its normalised around you. I remember her arguing that a woman she knew shouldn't be forcing her teenage son to iron his own shirts. I was absolutely flabbergasted. I also remember my lazy father would simply leave his jacket, plate, whatever he felt like at his arse in the house, and she would move it for him.
So I was alert to those obvious signs, but not to a man who didn't bother cleaning the bath or ironing his clothes (he'd go to work in unironed shirts when we were first living together, I didn't iron them for him but I did nag him into ironing them as it was dreadful looking). There were lots of little signs.
I do understand why young women who have always swum in a dirty fish tank cannot even imagine what a clean aquarium is like.
I do not understand why they pretend they don't have a choice when they've been putting up with his crap for ten years.
My ex husband cheated on me in the end and that would have been enough to end the marriage anyway.
But in all honesty the worst thing he did was to steal my unpaid labour, my peace and my time while I slaved away doing the jobs that had to be done because otherwise my kids would have lived in a shit tip. And I did argue and shout and beg and demand and try to discuss it while he hid in the toilet or did jobs slowly and sloppily. He was a lazy arse and didn't care how unhappy I was so long as he didn't have to do it - like so many men.
I would love to get all those thousands of slave labour back. But at least I didn't just put up with him steam rollering me quietly and come to mumsnet to ask questions, I never questioned he should be doing more, or blamed myself, or timidly tolerated it. I pushed back hard and forced him to do some of what he should have been doing without even being asked.
I find meek, compliant women irritating and I find it incredibly annoying that some just won't learn. I was always a stroppy cow, maybe it's nature to a great extent for many.
And my second husband does more around the house and garden than I do and is a fully engaged non selfish partner in life. You can, indeed, live and learn :)