In my experience, pretty much everything does indeed have a microcontroller nowadays (because software is so much easier to make, test and change than electronics, plus a lot of what took several digital components in the old days are just a few lines of code in a microcontroller, so putting a microcontroller there is cheaper also in hardware terms), but most things use tiny ones like the one whose info I linked in my previous post (if you get your hands on a broken mouse, open it up and google the part codes of the integrated circuits you find inside), with maybe a bit more memory since that specific ATTiny is very much on the lower end.

The reason why it's something like that rather than something bigger, is that something like that costs $0.38 each, in bulk, whilst something that's big enough to run Linux costs around $10+, plus something like that has a smaller physical footprint, needs all of 1 capacitor and 1 resistor externally for it to work and can work directly from some pretty shit power sources, further reducing overall costs, whilst microprocessors demand a lot more supporting electronics and proper power regulation to work.

When the cost of putting a big one there are nothing next to the overall device costs, manufacturers can easilly just upgrade it to "smart" enough to justify Linux (which goes beyond merelly digital controllers and displays or even WiFi connectivity and into Android TV levels of complexity) with little risk, but when we are talking about much cheaper stuff, they'll only make a "smart" version if there's explicity demand for such "smarts" that's willing to play a lot more. Notice how, when comes to dildos if you look at the Lovense which probably the most complex around, as somebody else pointed out it still uses a microcontroller that's not running Linux and is way too small for having Linux to be worth it even if possible - in fact per its datasheet doesn't even support WiFi but only Bluetooth LE, which means it doesn't even have an IP stack, as Bluetooth is basically Serial-over-radio, which means it's actually the software on the other side of that Bluetooth link that does the heavy lifting.

I think your idea of "everything" in Electronics is pretty much just big ticket Consumer Electronics, yet most Electronics out there by number of units is actually the small stuff that costs a few dollars in parts to make, and almost all dildos fall into the second category, not the first.