Because we don't want to live in a society that so strongly encourages "sacrificing vacations and eating out for 12 years (literally ate out 5x max)" and "My dad commuted 4 hours daily instead of moving."
I'm all about parents sacrificing for their kids, but when the system is set up to push people that far something about the system is broken.
We should absolutely want to live in a society that rewards people for effort and sacrifice. If we do not reward people for doing those things, they won't do them, and you definitely don't want to live in that society.
I wonder if the opposite is true as well. That is, when theses sorts of discussions come up, I'm always asking: when is it over? When does the sacrifice stop? A person sacrifices for their kid for some nebulous better life, which their kid goes on to do for their kids...ad infinitum? However, through an evolutionary lens it make some sense: an individual doesn't have to have time to enjoy any advantage they've accrued through such previous sacrifice because evolution doesn't care if you're happy, just that you're reproducing successfully, and so far that's instilled (it's arguable) an instinctive sense to socially rise in order to obtain better access to such. So in such a sense there really would be no point of it being over (except for the extinction of the species). So why shouldn't someone in this great chain of sacrifice say no and kick their feet up and enjoy the fruits of all that sacrifice? This would explain why we (society at large and various specific social groups) treat the childless so negatively and use the term anti-natalist as a slur.
However, there is another component to it: one's advantage is always relative to others' lack of advantage. This is why equal access education will never be truly supported (no matter what people say); if all kids have the same advantage as their kids, then their kids don't actually have any advantage at all (in social terms).
I think it's just a personal choice everyone makes. How much should they sacrifice now to have more later (either personally, or inter-generationally). We all have different preferences around that, and that's ok. If someone is willing to work harder or sacrifice more, it's reasonable for them to get more reward later on for their efforts. If you prefer to enjoy the present, that's ok too.
Did you skip what I wrote? You say you're all about parents sacrificing for their kids. But why would they bother if their kids won't get any benefit from it?
I'm all about parents sacrificing for their kids, but when the system is set up to push people that far something about the system is broken.