Some just need to get out of the house so they don't procrastinate by playing on the SKMB...
Also, to be taken seriously by others for what you do.
Say "I'm a writer" and then don't leave the house, and people assume you're just goofing, have a lazy bone where your spine should be, dabbling in a hobby, whatever. It's also taken that you are simply 'at home' and therefore available to whoever wants to drop by, for whatever purpose, there to take in unexpected, unannounced deliveries, and so on.
Say "I'm a writer" and go to an office or room elsewhere every day, you're taken much more seriously because you're seen to have
gone to work.
Which is a load of old [shoe-repairers], an outdated attitude and way of looking at the working world, but there it is.
Of course, if you work at/from home and complain that just because you're physically in the house you are not technically
at home...that's where the problems can start. And yes, this is mostly a personal experience gripe. The amount of times I've been interrupted and not been able to get back into anything close to the same working mindset and flow is ridiculous, but nothing changes.