A call to $this->logger->info() inside an entity looks harmless. It is one line, it does not change any state, and everybody agrees that logging is useful. Yet from that line on, your domain imports a technical interface, your unit tests need a mock to instantiate the entity, and the layer that is supposed to depend on nothing already depends on something.
A domain event describes something that already happened. It is a fact, not an intention. Yet many codebases publish events from inside the entity, at the moment its state changes, which couples the entity to infrastructure and lets you announce a fact before it is even true in the database.
A generic InvalidArgumentException tells you nothing about the business. It says an argument was wrong, but not which rule was broken or in what context. By the time you read it in a log, you are reverse-engineering intent from a stack trace.
Most PHP projects hardcode their ID generation strategy. Calls to Uuid::uuid4() are scattered across handlers, entities, and tests. When you need to switch to UUID v7 for chronological sorting or ULID for shorter URLs, you end up modifying dozens of files - and hoping you found them all.
Mocking a repository in tests does not verify your query; it only verifies that the method was called. Run a real database instead and the test suite slows to a crawl, so you run it less often. Either way, your filter logic ends up duplicated: once in the production code that hits the database, once in the mocks that bypass it. The two drift apart silently until a bug ships to production.