[UK-AL]

Actually I think this is a major advantage. They are not complexities, they are putting down into code how you think about your application in your head.

If your design is some data, which you can mutate however you want to get the job done, you don't really have model of the application.

Your business rules can become inconsistent because different developers are implementing different but similar methods in your business logic layer all applying slightly different rules. If the entities themselves enforce these rules, it become a lot less likely.