I'm no expert, but for awhile Bitcoin wasn't as high in price as it is now and it was actually too expensive for most people to mine because the electric cost was more expensive than running the miner would be rewarding. These days Bitcoin is surging higher and the value of the coin is enough that mining has become profitable again for a lot more people.
From my understanding mining Crypto is designed to emulate mining gold IRL, this is to say that it has to be worth x( amount to be 'worth mining' or enough to justify the effort put it and bring a profit; that or the technology has to improve enough to accomplish the same thing. Again though, I'm no expert.
Good points! I do wonder what the future holds for crypto when technology inevitably improves.