That's one of the big benefits of slack, but many organizations don't use it - you have to think to reach out to the person by calling or emailing, or you are scheduling a virtual meeting with something like webex.
I sometimes wonder if many of the "on-site only" employers even realize how much they are missing out on. For example, when I'm in the office, I work from 9 to 6, period. When I work for a remote gig, I can be working 12 hours a day without realizing it - my job literally becomes my life. I understand that it may not be very healthy for me, but isn't that every manager's dream? Yes, you have to make sure people like what they are doing, but that's a different problem and relevant even for onsite gigs.
Depends... are you working on the most important stuff first?
I'd rather have a strict 9-5'er that's always working in priority order than a 12-2am'er that's scattered and not delivering important work.
IMO the most important thing for success in remote work is having a prioritized backlog and defined iteration. It's way too easy to lose hours and days down an unimportant rabbit hole without these things.
I'd say many places don't have enough PM rigor to make remote work sensible.
Which, of course, it is.
Isolated: "separated from other persons or things; alone; solitary" [0], "separate from others" [1].
Remote: "far apart; far distant in space; situated at some distance away" [0], "separated by an interval or space greater than usual" [1].