Ok, so after the block size wars, people wanted to highlight the benefits of the block size choices they made by showing how one could make a node out of a raspi. And it's wonderful that you can, but it doesn't necessarily mean that you should. However, It kinda got "memed" into practice when it really meant to be a illustration of how good it is for decentralization to have small blocks.

It's, not a very powerful computer, if doing a few things at once, something bad (like overheating) might happen. But the biggest reason is the power supply. It's just done kinda cheaply. It's not really meant to be on 24/7 and it ends up leading to some fried SD cards.

Raspis have the advantage of being cheap. But they have been in short supply since the pandemic causing them to be not cheap enough anymore to be worth the diminished processing power and cheaply made design.