A basic stateless web app behind a load balancer can tolerate unstable network identifiers as long as you automate registering/deregistering the new names, which kubernetes services do very well.
Stateful apps can be a bit more exceptional because they often have client libraries that require you to hardcode network addresses via connection strings and other tooling that makes that glue automation more tricky and worth the added guarantee around consistent naming.
Stateful apps can be a bit more exceptional because they often have client libraries that require you to hardcode network addresses via connection strings and other tooling that makes that glue automation more tricky and worth the added guarantee around consistent naming.