Why?

I know of a museum with a huge Pi deployment and they don't have issues like that at all.

Museums tend to be climate controlled; factories... not so much.

It's not like they overheat and lock up in 4 hours, it's more like randomly in a day or two. But since they're just monitoring stuff every couple min, it probably felt safer to reboot all the time.

Not sure exactly about the decision process that went there, I just did part of the software running on them. But they definitely weren't stable long term.

There was a parking kiosk machine near my house that was using a raspberry pi. I only know it was a raspberry pi because it's often stuck in the boot screen with the raspberry pi logo at the top. My pihole runs for months without issue, but this kiosk was down really often. I wonder why, maybe the sd card is not reliable enough, or maybe it's the climate fluctuation like you mentioned because the kiosk is outdoor?

What I've noticed is they can run off 500 mA usb if you run them headless, but need the full 2A from their power adapter if you run X and usb peripherals.

So your pihole doesn't heat as much as the pi in that kiosk even given the same room temperature. And then, the temps inside an outdoor box in the sun can go way up too.

When I worked at Garmin, a guiding principle was “reset, and reset often”. Embedded products that you have to push out the door quickly have too much internal state to track.

And Garmin has some volume; I do custom industrial stuff that amortizes the software cost over a couple hundred devices at best.