Further, PIC isn’t the only “non-ARM” in this space. Your average RainBird type water timer likely uses an MSP430, for example.
The idea that ARM should be used in any/all situations is naive.
I mean, sure, this is true. MSP430s are great when you need the lowest power, and AVRs are tiny and cheap for lowest cost. But... I do this for a living, and there's a reason our go-to is the Cortex-M series. M3 or M4 if you need a lot of CPU power, or M0/M0+ if you need small. They're just so, so much easier to program that the trivial additional cost of the microcontroller washes away in the noise.
And it's not like this leads to Linux toasters; the M0 is not a microprocessor, it's a microcontroller. It's got a two-stage "pipeline" and absolutely no memory protection! There are tricks to get the larger M3s to run Linux, but it's hacky and not something you'd want to ship.
PICs are essentially obsolete, and none of us would ever consider them for new development. They're annoyingly constrained hoary old beasts.
No argument there.
No, it doesn't make any sense.
If you calculate you can learn one platform and use the knowledge and toolchain to produce wide variety of projects with less hassle it is difficult to defend using PIC for new projects when the only argument would be that maybe it uses less current in standby mode. The price is that you need to live with with essentially obsolete development environment with no future that you can use only for relatively simple projects.
We prefer to use PIC microcontrollers because they come in a DIP package.
Our products are mainly sold as PCBs that a customer assembles in their own home, appealing to the DIY electronics market.
For many, SMD is challenging, so having a DIP package makes us more available.
Additionally, the ability to use less power is useful because our products do not have an onboard power supply, instead relying on the rack's supply that may be shared between many products.
There are ton of other 8-bitters which have no need for paging -- Atmel AVR, MSP430, even modern 8051 clones and higher end PICs.
They all come in variety of DIP shapes and memory sizes, too. And great C-based toolchains.
I think that for the last ten or so years, there is no excuse for someone to use low-end PIC, the ones where you need to write "pagesel" my hand, at all. There is no niche where they are good.
https://www.mikroe.com/mikroc-pic
That said I wouldn’t use one for a new product. I think they could still have a place in education because of the quality of their data sheets and their robustness. In grad school we had a graveyard of ARM chips but the PICs put up with a really surprising amount of abuse.
ARMs from ST can run for years on a single AA battery and have nowadays very easy tools.
Probably you are missing understanding of whole range of ARM chips, these start from couple kB of flash and hundreds of bytes of memory.
Plus for the hobbyist at home, PIC still comes in DIP formats which is handy for breadboarding or soldering without the added difficulty of SMT.