Doctrine is project on it's own. Symfony sits on top of it. If you go that way, we can also say that Doctrine sits on top of MySql, and we can just write raw queries and forget about the ORM. You definitely can, which doesn't mean you should
Regarding your arguments and ours, I'm sure we could all be here until Christmas discussing the pros and cons of choosing either approach is, as both have them. We are not saying that your approach is without virtue, and ours without flaw. Like I told you before, this is the recommended way to do things, and I'm sure that people back at Sensio Labs HQ gave it a lot of thought before saying stuff should be done like this. If you really feel uncomfortable using service injection and/in controllers to do your logic, go ahead and inject services in your entities. It's just not the recommended way, and thus has the implications I mentioned before, but, in theory, it should work.