I'm sure there are various other options, but that's not the point. If you ask someone to take a supermarket salary and postpone their life till their mid 30s,then don't be surprised that people choose other paths.
The PhD programs I've looked at in the hard biosciences all provide a full tuition waiver plus a stipend with solid purchasing power for the area which definitely aren't "supermarket salaries" unless you're talking about management maybe. Maybe those people only want money out of life instead of to do research, but that's just my perspective.