>Well the RPI has GPIO
GPIO can be added via tons of USB to GPIO boards out there.
But I agree - lot of people tend to buy the Raspberry Pis for home servers instead of just opting for used mini-PCs from secondary markets. Even a 7-8 year old Intel CPU in those mini PCs will vastly outperform a Raspberry pi. Even the Raspberry 5. Plus, better I/O options and storage with mini PC.
> GPIO can be added via tons of USB to GPIO boards out there.
Depends on the use case. USB adds a few orders of magnitude more latency and jitter versus what's probably just APB.
Which only matters in very niche usecases though.
Most of the stuff just flashes LEDs or reads a switch. Doesn't matter for that. And for more intelligent stuff there's i2c or api which have their own interface boards.
Especially now that the RPI kind of need a fan and you need to buy the power supply, the storage and the case. Well the RPI has GPIO but for small home server use case nobody cares...