It's just that living with roommates is pretty frugal, and before the pandemic, it was a good way to save an extra $10k a year living in a more central location. Every single person I know who is a bay area SWE makes enough to afford renting a 1bed apartment in a good area, they just don't think it's worth it.
Yes if your main goal in life is to live in a large house on a large lot in a nice area without spending much, you will not find it there, but your characterization makes it seem like bay area engineers are poor which is... not true