Men are always told on here that if they don't want children then they should take action themselves and not leave it up to the woman, even if she says she's using reliable contraception. But I always think that if my DH did that in a long term relationship I'd take it as a sign that he didn't trust me not to lie to him about contraception
I remember a thread on here years ago where women were saying that if they were using their own BC and in a long term relationship that was monogamous, there was really no need for their partners to use condoms as well, and if they did it would make them suspicious of their motives. They would assume the men either didn't trust them to not get PG on purpose or that they were worried about an STD, meaning either they were being unfaithful or thought their partner might be.
That's problematic when viewed against a culture of women telling men 'no BC is completely reliable. If you can't accept an accidental pregnancy where I make all the choices then you shouldn't be having sex with me.'
This is only ever said to men. Never women.
I do understand why the OP is upset and bewildered, but I imagine when she says 'he wasn't 100% sure he didn't want more children' she's actually in denial about what's been said to her in the past. I'm guessing he tried to tell her he didn't want more kids and she didn't listen and he knew if he broached the subject of a vasectomy it would get shut down very quickly. Or there would be tears, begging and dramatics.
So yes, in theory it would have shown her more respect to tell her. But in reality it might also be understandable why he didn't.
Once it was done though, he should have told her. I'm guessing he was building up the courage to do it. I'm not sure how long it was between the op and her finding out.
But to suggest that she could have wasted all her remaining fertile years with him in the belief that they might one day decide to have more children and that is essentially tricking her out of the right to leave and have more kids with someone else, is a bit of a weird argument.
Most women (and men) don't leave an otherwise happy marriage where children (plural) already exist, just because their partner is adamant they don't want any more.
It reduces the marriage to nothing more than a baby making contract and it reduces the husband to nothing more than a stud animal whose only purpose is his ability to breed.