People do change, of course. And that's absolutely fine if both halves of a couple are comfortable with that change.
However, if you haven't signed up to be a sole breadwinner, then I think it would be pretty tough if your partner suddenly decided that they wanted to be a SAHP, and not unreasonable to say that you're unhappy with that. Same goes the other way - if you agreed before having kids that you would split the housework and childcare equally between you, then it would be pretty tough if one partner was expected to take on primary responsibility for all of that.
And indeed, same again if you agreed prior to having kids that one of you would be a SAHP, and the other person suddenly moved the goalposts and said that they were no longer happy with that, it might be pretty frustrating.
Ultimately, couples have to negotiate their way through these situations, but the bottom line is, nobody has an absolute right to opt out of paying their way, nobody has an absolute right to be absolved from any domestic responsibilities and no parent has the right to step back from their responsibilities towards their children. The default position if couples can't agree surely has to be that they share equal responsibility for everything.
In most cases, couples will hopefully have the communication and negotiation skills to work out a mutually agreeable plan between them.