OP - I can see what you're asking here.
On MN, there are a disproportionate amount of women who are in marriages, with children, who believe separate finances in a marriage / family is totally fine and normal. Some women have even convinced themselves that it's 'independence.'
But in all cases, when you get to the actual crux of the set up - it comes down to the same thing - ie, these women know, depp down, when all is said and done, that their DH would never share finances anyway.
Su they are left with a choice basically - either to convince themselves fine - it's 'independence' or whatever. Or leave.
It sounds to me this is the realisation you are having.
The way I see it is this - if a couple are going to share their DNA to bring new human beings into this world, the very first thing they should be able to do is share bank accounts! How can you be having kids if you can't even manage that?
There are some men (a lot on here, by the sound of it) who seem to think it's all fine and normal to do the 'my money, her money' thing.
It has nothing to do with amounts and who has this and that and what's fair blah blah blah. At the end of the day, it's a mentality. A deep rooted insecurity. At its core is an intransigent need to control... or something. Lack of trust? Lack of respect? Lack of commitment? Selfishness?
The fact is - in the eyes of the law, all marital money are shared. He can frame it how he likes, but that is the reality. It's so petty and pathetic to have financial divisions. You have children ffs! That ship has sailed. Who could be bothered with all this you pay for this and I pay for that?' You are a family! It all goes the same way regardless. You surely have the children's interests first and foremost. Who could be bothered?
You are absolutely correct that it comes down to some deep-rooted psychological issue on his part. Of course it will manifest in other areas of your marriage too. If you can't even share money - why bother? You are are essentially living as separate entities, not as a unit.
What happened to 'all that I am I share with you?' As if the wedding vows are - 'Well I'll do part-time and you carry on full-time and I'll pay this and you pay that and I'll have my money and you have yours.' What is the actual point?
Basically, I'm sorry you are in this situation. At least you're waking up to it though, which is more than a lot of women on here.
There's no point talking to him about this because frankly, it shouldn't need explaining. If he's an adult and hasn't grasped this basic stuff for himself, he never will. I'm sorry to sound blunt, but men like this are stunted and it's shouldn't be your job to help them function normally.