Absolutely, there is a point below which people just don't have the luxury to not take any extra work they can.
There is, however, also a large group of people who could have more free time but choose to work more because they prefer to own more stuff to having more free time.
I work an 80% job (4-day work weeks) because I have reached the point where I don't really need more money. I don't consider myself rich, but with my spending patterns I don't need to worry about a daily budget anymore, and I have cash leftover to save every month. A lot of people are genuinely surprised by this decision, even though they work the same kind of job as me and therefore many of them likely have a similar financial situation.
There is also a savings effect which makes making and saving more money start to have huge upsides. aka, if you live on 40k per year and make 60k per year you can retire young, but bump that to 120k and you can 'save' years as long as you don't let lifestyle creep set in.
They still (might) have the option of working less by not spending their money and retiring earlier. If you make $200k you probably can't work part time for $100k, but you can spend significantly less than you make and retire a few decades earlier than your peers.
I'd love to work 4 days. I currently work 5 and work in an industry (finance) where 4 earns you more than enough.
When I work 4 days with wednesday off, I don't even feel like I work... it's just a nice part of my life. On monday I think 'man it's been days since I did anything productive, I'm ready to get busy'. The next day I'm still in that flow, and the day after I've already got a day off. The same for thursday-friday, and then I've got two days off again.
When I work 5 days, on monday I feel glad to get busy again but I'm also dreading the fact that my immediate future is 5 days of work. By thursday I'm feeling like I could be productive working fewer hours, and on friday I'm really glad it's over. Further, my weekends and evenings are mostly busy with unwinding from work and preparing for the next working day. Whereas when I work 4 days, my free time is actually time for fun things.
I'm not a big spender, still on a 2010 iPhone 4 for example to give you a sense of where my priorities are at :p My money is slowly piling up.
So I could do without the money of the 5th day... but here's my issue... While my employer would probably allow 4 days work (which is not standard in and of itself, particularly not in certain industries), I KNOW that I'd be bottom rank when it comes to promotions. There's absolutely no way in hell I'd ever get a managing position working 4 days, at this company. And in a company of 5k, only the assisting/supporting roles have people working part-time. Supervisors or team leaders etc, all work full-time (or more).
I could stay in my current role forever, but it'd stop being interesting and intellectually challenging fairly soon, and I may develop some bitterness when I get to my 30s or 40s and start getting managed by people younger than me, just because they have a different vision on work-life balance.
So I'm pretty much stuck working 5 days, without being 20% more productive, earning money I don't need, because it's made abundantly clear that if you ask to work part-time, you can't ever work in a function of influence or leadership, at this company. And at most company's it's a similar story.
And I sort of get it... in a world of 5-days a week business and lots of people working 5 days, you wan't the manager to be present and available. Whereas assisting/supporting roles can be done by multiple people working part-time. It feels the only thing is left is either to be an entrepreneur or do something special (e.g. lots of jobs as 'special project officer' that's not tied to a m-f 9 to 5), but there's no standard path for regular salarymen to work part-time and still have a solid career in line with their productivity & competencies.
There is, however, also a large group of people who could have more free time but choose to work more because they prefer to own more stuff to having more free time.
I work an 80% job (4-day work weeks) because I have reached the point where I don't really need more money. I don't consider myself rich, but with my spending patterns I don't need to worry about a daily budget anymore, and I have cash leftover to save every month. A lot of people are genuinely surprised by this decision, even though they work the same kind of job as me and therefore many of them likely have a similar financial situation.