Yeah, at the cost of increased volatility. If two engineers, each with a 10% chance of losing their job in the next 2 years, do this then they both are much more likely (19% chance) to face uncertainty in that time.

They're all young. They don't think like that.

You may be missing the point. Say most tech engineers double up (as if they aren’t often doing this already). Guess what? You just significantly reduced demand for high-rent apartments

Renters will increase the price knowing full well that people will double up. Also if the renters are ruthless they would directly tell you to have more people packed in an apartment to pay their price and if people are helpless they would have to cough up or find some other job in another state where you can live decently with lesser pay. Also a lot of shitty apartments will increase their rents which puts more pressure. This I feel is simple price discovery at work. This is why it is better for the company to spread itself in different places rather than hole up in a single place and pay very salaries which are not sustainable. I really don't understand start ups which are supposed to be tight on cash sitting on one of the costliest real estate and expect to be profitable.