They do, actually. Charleston Road Registry (an entity owned by Google which also operates other TLDs like .APP, .DOG, and .FOO) is the registry; Google is the sole registrar. As far as I'm aware, all of the private TLDs operate on some variant of this model.

But it goes beyond just having those two distinct entities -- any ICANN TLD is expected to follow a set of operating policies (e.g. domain registration, renewal, transfer, expiry, and redemption; dispute resolution; WHOIS verification... etc) which is fundamentally incompatible with ENS.