My employer is pretty flexible. I have a fixed desk, as I am in the office most days, but there are lots of hot desks. I am currently working most Wednesdays from home to focus on a particular project. Other people have formal work-from-home agreement's. Plenty of people have agreed 3 and 4 day working weeks. There are certain roles which need to be on-site, so are less flexible, and some departments cover 24/7 shift patterns. My own department has an on-call rota, so 1 week in about 6, I could get called at any time of the night or weekend - but I get extra pay for that. We also have to do some maintenance work between midnight and 4am, but that's planned in advance, and you get TOIL. I don't have to be in at 9am unless I have a meeting then, as long as I work 40h a week. Others come in earlier and leave earlier. It means our commuting times are lessened, as the traffic is less busy - and we have people who are available for calls to AsiaPac or the Americas, depending on which end of the day. We have plenty of different communication options these days - phone, email, instant messaging, group messaging, video conferencing and so on, which means it's much easier to work remotely and still be in touch. It can work really well.
As one HR director used to say, "work is an activity, not a location." Of course, there are plenty of jobs where it is a location, and that limits the options for flexibility, but even then, there can be some options for flexibility, if you think creatively.
There are also people who take the piss, but that happens even when you have less flexible working, and it is part of management to deal with, however it manifests.