Dr. Mario on the ancient gameboy still runs without issue. Sure, it's a bit dated... but the hardware and the software for it are static.
A mobile Dr. Mario might only work until the next OS release. Spending $30 on something that may break in a few months is either going to be more costly to the company that created it (now having to do updates to it without any new revenue to support those updates) or brand damaging.
Nintendo is reasonably conscious about avoiding brand damaging things.
Long term support has never been a priority for nintendo. They don't want you playing Dr. mario on gameboy forever, they want you buying their new device every year and the new pokemon that comes out with it, so you can catch a pidgey like you did 25 years ago but you've payed like $2000 over those 25 years buying each hardware release in the process to do what is basically the same thing.
There's plenty of games where that happens on os and you see devs abandon them. Even still in gaming in general, gamers don't really expect long term support. Sometimes mulitplayer servers are shut down even when there is still a community using them. Some developers flat out say "we aren't patching this game anymore, its too old." Its the nature of the gaming market to keep buying the new game in the IP.
A mobile Dr. Mario might only work until the next OS release. Spending $30 on something that may break in a few months is either going to be more costly to the company that created it (now having to do updates to it without any new revenue to support those updates) or brand damaging.
Nintendo is reasonably conscious about avoiding brand damaging things.