In short, because of how DNS servers work.
Each TLD has to be resolvable in the root servers and as far as I know ICANN doesn’t manage root DNS servers and ICANN would have to become a registrar and coordinate all those TLDs with all the root servers all over the world.
In short, because of how DNS servers work. Each TLD has to be resolvable in the root servers and as far as I know ICANN doesn’t manage root DNS servers and ICANN would have to become a registrar and coordinate all those TLDs with all the root servers all over the world.