My question is who do these high fees benefit?
Miners and third-party service providers such as centralized exchanges and casino platform because these platforms usually charge fees higher than the usual network fees, so if the fees are high, they tend to have increased fees for withdrawals in that particular asset, in this case, Bitcoin.
There are a couple of key points to consider: First, If miners can change Bitcoin to increase the fees is Bitcoin really decentralized? Second, and most importantly, do these increased fees help bitcoin to be a better form of digital cash?
Who said miners can increase the transaction fees? Miners have no other role in the network than confirming and mining blocks containing transactions. Bitcoin doesn't work on a PoS consensus where nodes with the highest stakes in the network get to govern the network and take part in certain decision-making.
About your second question, of course not, high fees would never help any asset to become a better form of digital cash because the general population would never want to use an asset that charges a lot of money in fess for making normal transactions.