Generalist doctors have a median salary of ~$200k, with specialists earning a median salary of ~$300k. The lenders will have an easier time vetting doctors since almost all of them make a high income with good job security.

By contrast, developers have a median salary of ~$95k nationwide and ~$110k in San Francisco according to Glassdoor (or $65k nationwide and $103k in San Francisco according to Payscale). Of course, some make much more, typically through stock options. So lenders are probably filtering by occupation and employer (e.g. Google, Facebook, etc.).

I'll trust that the lenders are competent to determine whether someone with with a ~$150k salary is a strong candidate to buy a $2M house with no downpayment. Housing lenders haven't shown poor judgement in the past (edit: /s).