What I think you're missing here is the role of ambition. Full time on coding might make some people happy. That can happen if you only care about coding as an activity, and not about reaching specific goals. It can also happen if your goals fit within the amount of coding you can do individually in whatever milieu you're doing it. What if the thing you want to do, the software you want to create, requires more than that? Then you have to pull together a team, which brings in a whole bunch of complexity and loss of control. It can be awesome, or it can be draining and frustrating. Sometimes it's both.
On the flip side, "full time at home" isn't an option for many (probably most) people who'd be reading your comment or mine. Somebody has to make some money, not for its own sake but to reach family goals - housing of a certain quality, schools, sports or hobbies, whatever. Then there's a time commitment on top of that. It's a lot with one kid, it's more with two or three, it's far more if any of them or ill or troubled or disabled.
For many people, just having to choose is frustrating. People want to have a successful career and a good family life and time for themselves, and they just can't have all of them. Giving up on "having it all" is really really hard, and it's not immature. In fact it's the characteristic struggle of mature people, leading to burnout and mid-life crises. It's the immature, with fewer commitments and simpler goals, who seem least affected.
That's (part of) why I think your "that's immature" is itself the most immature thing I've ever seen on HN. It shows a startling lack of empathy for people going through something you apparently never have. I hope you are young, because if you can still say such a thing from the vantage of experience that's even more pathetic. The struggle is real, and being laughed at or condescended to as you go through it doesn't exactly help. It's part of what Jesse was warning about.