Note: this also assumes you're single and have no kids.
If you're two engineers without children - sure, you can afford to save that and buy. But remember - you still have that expensive morgage to pay off, even in an economic downtown. With rent you can at least move. With a morgage, you have to sell, and .. let's just say, being saddled with a black mark for needing to default on your home sucks.
If you're two engineers with children - then childcare per child from 0 -> K(indergarden) is spendy - $1400 a month upwards per child. At some point you think sure, I'll just get a nanny for two kids - but $3600 a month isn't a lot of money to be paying legit to someone who also lives local - if your rent is $3k a month, then anyone local is likely also paying that. So, finding affordable help is hard. So - one parent is effectively working full-time to subsidize childcare - why not just stay home instead?
If you're a single parent raising a child, then you get the above and no financial safety net.
Stuff is expensive out here. Raising that much cash is expensive out here. Holding a $600k or more morgage when the economy tanks - that's also an expensive lesson to learn.