By "everything that mattered" I guess I should have said "everything that mattered that you have a shell on".
For some of those non-desktop-operating-system devices, getting a shell is impossible without bypassing lockdown measures. For others, it's possible, but not particularly common as far as I know, for a variety of reasons. They tend to run stripped-down OSes; they don't have great keyboards; they were pretty slow compared to desktops until recently.
Yes, this is a huge overgeneralization. Plenty of people do run shells on their phones or routers. But I do believe that a major desktop platform switching to ARM is qualitatively different from what we'd seen before.
The EeePC was x86, the Chromebook Pixel was x86 along with many that followed with balance being ARM variants.
More recently you have convertibles/ultrabooks and their stripped down cousins (e.g. Microsoft Surface Pro vs. Surface 3/Go/Go 2 and Surface 2, Surface RT, and Surface Pro X the latter 3 being ARM).
Ultimately the netbook niche has been squeeze by ultrabooks and tablets to few offerings if anyone is even bothering to market computers that way anymore.
This is revisionism. It ended with the smartphone and netbook era, both of which put more ARM devices in homes than Macs ever will.