You then have the flexibility to just get up and walk into a meeting with it or walk out at the end of the day with everything just as you left it and carry on working on the train should you need.
The most recent ones also half a decade old and still quite expensive, so I can't imagine buying one, but Apple would tell you that they do have a first-party docking station, complete with monitor built-in!
When I was a die-hard Mac user, that was perhaps the only thing that I wish Macs had, minus the crashiness that docks caused on Windows.
Using an external keyboard and mouse solves the ergonomic problems of using a laptop for long periods. (Sad to say, I see very few people actually doing this.)
Of course, you don't get the benefits of running a faster, hotter processor, expandability etc, though Apple no longer offers a reasonably priced tower system anyway....
But moreover, a PC forces me to do my work in a place I have dedicated to work. People are now recognizing the importance of sanitary sleep habits. Well, my PC helps me maintain sanitary work habits. Well, it did when I was working from home a bunch.
I started a new job a couple months back, which has me working from their offices on a shiny new Mac Book Pro. I hate it. I've grown to love the efficiency and instantaneousness of everything on my utterly predictable libre *nix desktop. Plus, even if I don't plan to do work outside working hours, there's a strong corporate culture of taking your laptop home--I don't know, to maintain optics of always being working or something. Either way, my employer could have saved a few dollars and made me much happier by locking a workstation to my desk.
In less than two weeks I already have neck and back problems from hunching over my laptop all day. Thank god I only have two more days of this insanity.