I come from a country excluded for betfair. I am irritated by betfair brokers, it's not the same. There is no worthy alternative for them. Why has no one built something similar, based e.g. on BTC? Isn't it a profitable business? Is it worth it to ban an account from an allowed country? I have doubts, most of it is probably a scam, and after some time it can be blocked anyway.
Have you taken a look at BTC betting exchanges like Fairlay?
Whilst I agree that Betfair is definitely a great service, it's not the only fish in the ocean.
Take a look at both centralized sportsbooks like Nitrogenbet/Sportsbet.io etc. as well as Fairlay - and I'm pretty certain that there is actually a few decentralized betting markets (that don't have much liquidity within them) hosted on blockchain as well.