I think it's mostly a combination of the work culture at any given employer or even within a team, and the habits/expectations of the people doing the work. I

I think it's mostly a combination of the work culture at any given employer or even within a team, and the habits/expectations of the people doing the work. I keep weird hours due to working remotely and across time zones, and I do encourage people to contact me by phone for anything time-sensitive when I'm offline. But that almost never happens, people are usually OK with waiting until I get back online to answer their queries. Some form of this is more the rule than the exception on my team, because the people who don't work remotely still have lives (pick up the kids, avoid the rush-hour traffic, whatever) -- and also have to be flexible about their hours due to the multiple time zones. This includes people with 1 to 25+ years experience FWIW. So I wouldn't worry about it, if you want to have a strict 9-5 boundary you can find good places to work (just not on anything mission-critical). If you prefer to work 40 hours a week on some other reasonable schedule, you can also find good places to work. I once had a colleague who worked a very strict 9-5 and could have been called in an emergency but we all understood it would have to be a REAL emergency before we bothered that guy. He did a great job and everyone respected him, despite his being probably the only guy in the building keeping such a rigid schedule.