- They're a founder
- They're a spouse of a founder
- They're a friend of the founder
- The worker is unskilled and needs to work crazy hours to break even
- They believe in the company and have equity
- The vertical is more politically compatible than alternatives
- The vertical punishes newbies before the career starts paying off (lawyers, doctors, academia)
- The work is interesting/fun on its own (in these cases, the type of work would never be paid well -- teaching, charity work, homemaking, niche tech, etc.)
- The worker is being compensated in other, non-monetary ways (aside from equity)
- The job is poorly paid locally but well-compensated elsewhere, and moving/remote work is not possible
Are such people idiots? Maybe.
That said, people who place money above all other factors trend closer to the "idiot" line, in my book. YMMV.
If you require the literal best pay possible, you'll be job-searching forever. Some people do not have that luxury.