Hey Tichy - good questions. Never thought this post would end up on HN, so I didn't explicate the problem(s) and challenges systemically.

There's no universal law, but as mentioned earlier, there is a cultural norm, or, as patio11 pointed out, a tendency towards social pathology that rewards 'overwork.'

All startups may not require the long hours - I don't know and can't speak for ALL founders. However, I know many for whom this is true. It's certainly true that in this stage of growth (pre-toddler) for MY startup it requires that amount of work to complete the specific things I have on my calendar.