I don't mean to generalize, but I've never seen this same mindset in people of my age (lower 30s).
I was having dinner with my mother and a friend of ours who recently retired, and the subject of work arose. I have a job that requires very little from me for most of the year, and I'm fortunate enough to have bosses that don't care if I'm engaging in my semi-lucrative hobby of writing during the parts of the year when I'm not busy.
I mentioned that other people in the company think I'm wasted in my role there, because I could do more work and be more challenged if I wanted to. My mother's friend agreed that I'm wasting myself there, and that I should be doing more than “coasting” through work.
I explained that work isn't my passion, writing is, and my bosses are well aware of that. Why should I leave a job that pays me an okay salary and gives me all the time I want to pursue my passion, and trade that for a job that may not pay as well and would likely be more mentally exhausting, just because I shouldn't coast?
Later, my mother agreed with her, that I'm wasting myself, but I don't see it that way. I prioritize my mental health and my own creativity over working a job that would suck the life out of me, and I don't understand why older people think that's wrong?