That seems like an overly cynical explanation. There are many reasons why you would want a service instead of a library:
1. Even if the service is just a CRUD API, then you can isolate the storage layer from external users. If you just a have a library then every application needs to be able to connect to the DB.
2. You can protect mission critical resources through rate-limiting in a way that is way harder with a library.
3. Even if those are not problems, if someone has a DB connection then there is nothing really stopping them from just going around your library entirely. So random service X gets popped by an attacker. Now they can execute arbitrary queries against your DB. With a service they are still constrained to the operations exposed through the API.
4. You have a lot more freedom to change internal implementation details for a service. Need to change your DB schema (or migrate between postgres and mysql) then you can hide that behind the service interface. If you have a library out there then you have limited control over when people take version updates and it is virtually impossible to synchronize the update across all consumer of said library.
1. Even if the service is just a CRUD API, then you can isolate the storage layer from external users. If you just a have a library then every application needs to be able to connect to the DB.
2. You can protect mission critical resources through rate-limiting in a way that is way harder with a library.
3. Even if those are not problems, if someone has a DB connection then there is nothing really stopping them from just going around your library entirely. So random service X gets popped by an attacker. Now they can execute arbitrary queries against your DB. With a service they are still constrained to the operations exposed through the API.
4. You have a lot more freedom to change internal implementation details for a service. Need to change your DB schema (or migrate between postgres and mysql) then you can hide that behind the service interface. If you have a library out there then you have limited control over when people take version updates and it is virtually impossible to synchronize the update across all consumer of said library.