not only does a founder capture more upside, they also pay less of a cost. autonomy prevents burnout even under very intense working conditions.
plus the nature of a founder's day to day work is very different. 12 hours a day of management, pitches, meetings, and snap decisions is doable for a long time if you can endure the pain.
12 hours a day of complex technical work under sleep deprivation is just not possible, after a few weeks of this your cognitive function will decline to the point you can't do the job right.