my limited knowledge on the subject: mining caused an explosion of prices of GPUs. If you didnt know, GPU mining is far superior in hashes than CPU mining. Now there's something else called ASIC which is specifically for Bitcoin. I'm pretty sure ASIC mining can't be used mine other currencies like Ether. Bitcoin Gold was a fork to attempt to solve the unequal distribution of mining, like how a small % can make up more than 80% of the total mining around the world. Now with a concept of Proof of Stake other than Proof of Work, crypto is still trying to figure it out. Most of the bitcoin has already been mined already with about 2 million more left until 2020 where after that, the blocks will reward only 50% or so.