Those can listen to database changes and aren't separate services to set up, keep online and pay for? Neat (and news to me)!

Except if you disconnect for any reason, you will miss changes. If you want to break out services into different servers, clients will still be crossing the streams to listen. Database schema changes must be coordinated properly. Basically, you are taking one database to rule them all model which comes with massive drawbacks and inserting additional capabilities into it.

Sure, if you are tiny, will forever remain tiny, then whatever, ignore this Ops person.

Please check out the linked libs, this is not true (and dig deeper into Erlang/Elixir). The schema change issue can be tricky, however.