I don't understand how people do it either, and I'm someone who works every day for 8+ hours in a metal casting plant. A sweatshop basically, for barely enough money to afford expenses. Luckily I'm pretty frugal since material things don't do anything for me. The best explanation I think I could give you is that we're forced into it out of necessity. I'm given a choice of freezing in my car or living in a small apartment where at least I can be on my computer. Honestly, I feel like life is just trying to distract myself from the fact that I have to work, then keeping my head down and just pushing through each day.
I think others are content since they may have meaningful and fulfilling careers they can enjoy and barring that a meaningful life with friends, hobbies, and families, but not everyone has that. For those who don't, we're consigned to wage slavery. I like to think that one day I could build something, but that's something I've told myself since 3rd grade and it hasn't yet come true.
It seems that a lot of living life is doing stuff that is necessary survive, but not necessarily what you want. Worse still, is when you don't know what you want, don't know if you are capable of wanting, and are unsure of what is necessary to build your life.