> everything the pi is touted to do, you can either accomplish with existing general computing or something like an arduino (and as a benefit, learn some electrical theory as well.)
This may be true, but was it true when the Pi was released?
For me, the Pi sits in an uncomfortable position where it's not really the best at anything it does. It's promoted at being for education, but arguably there are better solutions, and almost certainly the overwhelming majority of Pis purchased are by individuals and businesses, so this is a kind of misleading advertising.
They included a chip for media decoding (including 4K HEVC), which is a dead giveaway that much of the draw isn't the education market, but it's shockingly limited. For instance, despite support for HDR being advertised with the release of the Pi 4, as far as I know it still doesn't work at all. High bitrate media often fails to decode in real time. So if it's a HTPC type use, you'd be much better served by an Nvidia Shield or something like that.
The emphasis on netboot support suggests that they envision enterprise use cases, but it took them forever after the Pi was released to have this working fully.
They include hardware design files that suggest it's designed for the hobbyist hardware market, but yet it's not truly open hardware at all, and in fact they've been drifting further away from that ideal over time.
If anything, the niche is probably tinkering with hardware (given the number of add-on products), without having to jump in all the way with an arduino, but how many people who buy a Pi actually end up doing any of that? In the end, I suspect a lot of people bought them for the novelty of a $35 Linux computer.
I say all that, but naturally I own 3 of them myself. :-)