Because CORE lied to you and segwit doesn't do shit to scale Bitcoin, even for the short term. CORE's goal is centralize Bitcoin by introducing Lightning Network.

Super expensive on chain fees are their method to push you to use LN and doing offchain transactions, since they will be a lot cheaper. CORE doesn't even hide the fact that they will turn Bitcoin chain into a "settlement network", only affordable to the operators of LN nodes (eg. corporations).

Bitcoin Cash backers (eg. big blockers) were right all along, bigger blocks were the answer to scale Bitcoin and have sane fees.