I assume that SegWit is so perfect, but why most miners refuse to use it? It is 3 months after SegWit released, but only 20% miners agree to switch in SegWit mode, what is wrong? What do they think?
Miners agree on enabling segwit and mostly malleability fix IF the Core client also remove the the current block size limit.
They aren't enabling it because segwit leaves the block size limit in the hand of the devs of Core, and miners don't trust them and their promises anymore.
So, the Bitcoin Unlimited team is trying to give miners what they've requested. (and also
segwit fixes)