I'm convinced that decentralized communities will eventually corrupt and destroy all centralized services and agencies by manipulating their employees and members... Because they can. People will always find a way to create new problems to make themselves necessary. In these political games, decentralized anonymous communities have the upper hand. Unlike centralized projects, you can't corrupt decentralized projects. What can be corrupted, will be corrupted.
To understand why it's the future, you need to look at the big picture. You're assuming that centralized auth providers are secure and trustworthy. This is not going to be true in the future. Trust in institutions and organizations has been eroding and will continue to erode.
“Services will make more money because blockchains are trendy” isn’t a meaningful difference.
I cannot possibly imagine a world where services will choose to only permit authentication via some expensive blockchain such that they deny themselves access to markets outside of the global rich.
And telling my grandma "don't worry, the coins you don't understand will go up in price" is not going to help.
This is the core question: why is signature-based authentication using public keys associated with BTC wallets superior to signature-based authentication using public keys not associated with BTC wallets? As far as I can tell, the only benefit here is that now my identity on my photo sharing service can be linked to my identity on my wine rating service. Why do I want that?