Companies want to sell what consumers want to buy. But the average consumer doesn't want a general-purpose computer for this job; they instead want to buy a "router".
If companies market the devices as something other than "routers" then consumers will not buy them for routing duty.
(Meanwhile, the non-average people who want to use general-purpose computers as homespun router/NAS/do-all boxes are already aware of how this all works...and many of us have been doing it this way for decades. (Often, this happens alongside dedicated access points that do have good wifi radios.))
> But the average consumer doesn't want a general-purpose computer for this job; they instead want to buy a "router".
So start your own company called usa router co, and sell some random arm board with a preinstalled router image... the end user won't know the difference.
The average consumer doesn't want a router full stop. Their ISP hands them an all-in-one modem+router+switch+WAP box and they just accept that the internet lives inside of it.
I have roommates who are engineers and I had to explain to them the difference between Wi-fi access point and LAN when I replaces our wireless router with a router + 3 APs.