Performance per Watt still outranks any other (quasi-)mainline linux device
Many years ago, I measured performance per watt of the original Raspberry Pi when they were still relatively new. The performance per watt lagged behind even a beefy Intel box since the original Raspi was so slow that it destroyed any gain it got from using so little power.
EDIT: One set of benchmarks I found as an example: https://bret.dk/raspberry-pi-5-review/#Performance-Per-Watt
They've never been particularly cheap, in a performance-per-dollar sort of way. Used machines from eBay, yard sales, and old broken laptops (that still compute!) have always been better. (They usually come out OK when new is compared to new, though, which is IMHO the only valid comparison.)
Those comparisons were never very favorable.
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The parts where it shines are: Small; they come in two sizes, and those sizes are small and smaller. That was new, but it's been cloned all over the place.
Built-in GPIO that's meant for people to actually-use and tinker with. That was new, too, but it's also been cloned. (Also: These days, anyone can plug a cheap Pi Pico into any PC with USB and get a fairly intense amount of GPIO to goof with.)
Standardization, and the appliance-like behavior this can enable. Lots of folks, including kids of all ages, just download pre-built images and swap SD cards like they would cartridges in a Nintendo. That's not for me, but it's pretty neat.
Community. They've still got a lot of momentum by being first at these roles. That's good. It helps newbs (who at this point may have never had anything resembling a "real computer" to play with ever before in their lives) to get started.
Low-power enough: It's not ideal when chasing tiny Watts for battery or small solar power, but you probably won't notice it on an electric bill (and despite the bizarro-world cooling rigs people put together, a passive heatsink really is good enough to keep it running in-spec).
but there is very little reason to use a rpi over other sbcs if you have a remote idea what you’re doing beyond hobby use
If you don’t specifically have a project where you need the GPIO pins built in, I struggle to understand the use case proposition of a raspberry pi compared to a typical x86 mini PC or even just grabbing a think client desktop like a ThinkCentre.
Almost everything that is unique to a Pi compared to an x86 mini PC seems like it makes more sense with an ESP device.
When the Raspberry Pi was $35 and it ran a desktop OS and the cheapest alternative that did that was 5x the price that use case made sense.
The ones I find on Lenovo's website don't seem to get any cheaper than $649.
Or do a search for “mini PC” on aliexpress.