I've been in the situation (before I went back to work two years ago, when DC4 was 3yrs old) that I've been told by someone how lucky I am that I don't have to go to work, and that I should be grateful that DH can afford for me not to! 
I agree, and acknowledged it, but also felt a bit
and even a little
.
If I'd had a fantastic career/well paid job before DCs, and my salary had played a big part in our getting a mortgage, I would have gone back to work, and probably wouldn't have had a choice.
The fact is, I didn't have a good enough job to begin with
that would justify me going back to work and paying for childcare
. Quite the opposite of what the person thought, iyswim. That's the only reason I had to was able to stay at home.
Yes I've been lucky, that DH's salary could support me and our 4DCs. Other people I know have gone back part time and have have had their parents/pil look after the children for them. Maybe if my DC's grandparents had been knocking down my door, prepared to put in the hours that other peoples' are, I'd have been able to work PT sooner. There have been plenty of times that I would have liked to be in that position, and have the disposable income that they have.
Similarly, people who I know, whose parents rock up at 7am so that they can go to work, and are there to look after them, cook everyone's tea, and hold the fort till mum/dad come home at 5:00/6:00pm, might have had to be SAHP, as they might not have been able to afford to go to work otherwise.
Having said all that, I am grateful that I was able to be at home, but also a bit
that it wasn't a choice, and I'd have loved to have worked part time sooner. I would hate to be in the position where I had to work FT, I'm not cut out for that at all.