They are buying them for children (to avoid malware and viruses and the general cruft of maintaining an OS), and for themselves (because, again, viruses and cruft).
Meanwhile, this OP may well be about a very expensive Chromebook but the other killer advantage of them is they're very lightweight, have very long battery life, and are VERY cheap. If you're sick of Windows and the fact that it just gets slower and slower over time (and everybody is), and you're not the sort of person who has 30 tabs open (which is more or less everybody but us), and you actually need to have a device you can type on, then they're great.
I recommend them to most 'civilians' I know after making sure they don't actually need one of the few things it can't handle.
If I were to buy a second computer for travelling and lightweight stuff at home, and not developing, I guess a Chromebook would be a nice choice. But not at the price of a Macbook Air, though.
I presume they're not getting the Pixel models though. I don't know who buys those.