For those not clear, AppleTalk was created at a time where there was no universal standard in networking. The “standard network” you think of today, a bunch of computers plugged into a router, existed but wasn’t the de-facto setup. There was still experimentation going on.
Apple ported some of the AppleTalk features, such as Network Discovery, into Bonjour which was introduced in 2002. Once that became mature, there was no reason to keep AppleTalk around.