I second that. This practice comes from a time where domain names were expensive, in many ways: SNI didn't exist/wasn't wide-spread, so each domain name on HTTPS needed a dedicated IP, Certificates weren't democratized yet via letsencrypt/acme and most hosts were big enough to run multiple services, because virtualization wasn't as widely available yet. So putting apps on sub-paths made sense.
Now all of those things are basically dealt with and putting each app on its own sub-domain just makes way more sense.