It's industry best practice -- not a joke. What's more, the recommendation is to have a separate database per service -- one table, one service, one database.
Fuethermore, when a join is desired, the best practice is to implement not just a service that joins the data but maintains it in a table/materialized view of its own, along with a message server such as Kafka. The services responsible for the tables to be joined (customers and orders, for instance) put events on this message bus which the joining service subscribes to in order to know when to update its view. See: https://microservices.io/patterns/data/cqrs.html
