Why could we do that? because in the end it is a work for roughly 5y and if you stop even thinking about working 24x7x365 you have enough free time for recreational activities. I'm on vacation around 6 times a year, but available to the company on critical stuff.
Yes sometimes it's hard, sometimes you have so much work that even 24 hours a day wont be enough, but then again you need to focus on the important work and think about yourself.
Btw I only did the bootstrap way with every company founded on 25k€ and no VC/Angle/Bank/External money and very low income in the first years (I hire people ASAP). As of today, in average over the last 20y this gave me more then 500k€ yearly salary with the exit money. Not bad and definitive much better than I would have had in in any Employment.
For me it is absolutely no choice to be employed or working in larger companies. I want my own freedom :)