Too many companies (even startups) are conservatives and traditionalists in the sense of thinking that work needs to be done within certain hours and at a certain place, even when those are not drivers of the results.
I'm hired to deliver certain results, not to work a number of hours. If it takes me 10 hours or 40 hours to deliver those results, that's up to me, as long as the deadlines are hit and the deliverables are high-quality. And there's no reason to be in an office, unless the office is instrumental to achieving those results.
The focus on how many hours people should work is a fetish that reinforces a still-dominant 20th century office culture.