Maybe this is a very simple matter to you, but my stupid head is still confused as to why bitcoin mining has shifted from CPU to GPU and now to ASIC miners?
I know there is limitations on block size like an average 1megabyte for per block. So what's the issues there so that force to upgrade the miners?
The block size hasn't increased here, so miners need more powerful hardware.
Then what the cause for shifting?
The major reason behind what force the shift of the Bitcoin mining rig from CPU-GPU-ASIC is the level of mining competition, and for miners to mine profitably, they need to use a mining rig with good computing power.
It's just like you working as a freelancer and you're using a 2G internet when other freelancers are using 5 G. You won't deliver your service to clients on time, and you'll lose clients while others with strong internet deliver their service early and gain more clients.