It gives them the option of portability, plus doesn't tie them to a physical seat in the room where that desktop may reside.
Good example: For the better part of 25 years, my primary computer (browsing, music, news, communications, etc.) has been a Linux box that I built from scratch. Motherboard, memory, CPU, PSU, case, the entire lot. Build it, install my distribution of choice, and off I go. For any gaming (and I really wouldn't call it that; I flightsim), I use a PC that I build from scratch.
Well, you can see where heat can build up, and that tying me to the seat in front of the monitors I use for the entire time I'm using them. Fast forward those 25 years, and we have our first child. Well, sitting in front of a Linux box, compiling everything, including the kernel, all security updates, etc., gets really time consuming, especially when all I want to do is play with my child and be a father. So all the tarballs I've had containing the source code for everything I compiled get archived (in that process I find all of my personal files use 120GB, and that's out of a 12TB Linux box I had), Keep the PC, and drop to a 256GB 13" MBA for my primary desktop.
That gets me a Unix OS (like I had in Linux), a GUI, all my personal files, and gains me portability. I could web surf sync my phone, and work on any paperwork I have for my business, all from my child's room while rocking them to sleep.
So no, not a bad idea, when you gain the portability as well as have it for your main computer.
BL.