If you've got centralized account management, it can work. Sending a fixed length 16-bit numeric id rather than a variable width username is a lot easier.
I've worked somewhere with a lot of NFS, and they had centralized account management, so everything was fine other than actual security, at least until we hit the limit of 16-bit uids. That place had a different centralized account management for production, so uids weren't consistent between corp and prod, but NFS in prod was very limited. (And you wouldn't nfs between corp and prod either)
I worked somewhere else without real centralized management of accounts on prod, and it was a PITA to bring that back under control, when it started becoming important. Even without intentional use of uids, it's convenient that they all line up on all servers; and it's a pain to change a uid that already exists on the system.
I've worked somewhere with a lot of NFS, and they had centralized account management, so everything was fine other than actual security, at least until we hit the limit of 16-bit uids. That place had a different centralized account management for production, so uids weren't consistent between corp and prod, but NFS in prod was very limited. (And you wouldn't nfs between corp and prod either)
I worked somewhere else without real centralized management of accounts on prod, and it was a PITA to bring that back under control, when it started becoming important. Even without intentional use of uids, it's convenient that they all line up on all servers; and it's a pain to change a uid that already exists on the system.