I'm not sure it always works that way. I know quite a few of my SAHM friends chose to be a SAHM precisely because their parents were both FT WOHPs and they didn't find this ideal from a child's perspective.
Yeah, I think you're right that people don't just follow the example set by their own parents. I'm sure that a lot of SAHMs do indeed make that choice because their own mothers struggled to find the right balance as working parents - after all, things were a whole lot tougher for working mothers a few decades ago, and it would have been much, much harder for many of our own mothers to balance home and work as effectively as many of us can now.
Similarly, I know a lot of WOHMs who are absolutely determined to maintain their careers after having witnessed the impact on their own mums of staying at home. Many of us choose to do things differently from how our parents did them, and we're often encouraged to avoid making the same mistakes as those in the previous generation. I know my mum would have been devastated if we had made the same choices that she did.
I think a lot of it boils down to individual experience tbh. If your own mum was a SAHM within a stable relationship with no financial problems and found this rewarding and fulfilling, then it's likely that you might consider being a SAHM as a viable option. If, on the other hand, your SAHM parent was bored, frustrated and unfulfilled, and hated not earning her own money, you might feel differently.
And if your WOHM parent was constantly stressed, distracted or just plain absent when you were growing up, you might not think that having two parents with careers is in the best interests of the children. If, on the other hand, you have grown up in a home where both parents are able to balance fulfilling careers effectively with home and family life, you will probably take it for granted that you'll do the same.
FWIW, I don't agree with those who say that the OP is being hypocritical because she was a SAHM herself. Her opinions are based on her own experience, as is the case for most of us. It isn't unreasonable to hope that our children might take a different path to the one that we have trodden. However, for the most part, I think we have to keep those hopes to ourselves and support the choices that our children make for themselves. That's not to say that we shouldn't share our own experiences with our kids, including any regrets that we might have about our lives. Ultimately, though, we have to let them make their own mistakes. And they will....