Linux

It's more complicated than sheer greed.

The fact of the matter is that actually producing any modern technology takes a massive amount of work, and up til this point, no one has gathered enough motivation and free time to do it all for any modern hardware just out of pure altruism. There's a reason why companies have to pay hundreds of engineers a huge amount of money to get anything developed; those people are not going to do this incredibly difficult work just for fun and moral satisfaction. It's easy to point the finger at corporate greed for some things being locked down, and to be clear, there's plenty of valid criticism to go around, but it has to be at least considered that most of this stuff would never have been developed in the first place if it wasn't for those same companies. Your average person is not going to assemble a motherboard from parts and schematics.

Wouldn’t anyone just be curious to figure out how stuff works?

To this point, quite frankly, no. Average people simply do not care about this very much. They want to just turn on their magic internet box, get their work done, play their games, consume their media, and move on without any further fuss. The fact of the matter is that most people have no clue what a BIOS is, could not care less if it was proprietary or not, and have zero interest in learning about flashing them or why they would ever want to do that.