Why do people think that because max block size 20Mb = ALL blocks will be 20Mb?
can someone please explain this?
Because some people are idiots or have their own agenda. It's that easy.
Nobody has said "ALL blocks will be 20Mb."
But what if they were? Nobody knows, so we should gather enough data to make informed predictions and preparations.
Right now, there are so few full 1MB blocks that we have no idea how the system would react, especially to much larger ones.