PHP框架中的MVC架构：是否有必要使用DAO或Repository模式？

In my new job, they use (don't ask me why) a custom framework that is based on MVC architecture. Myself, I have a lot of experience with Symfony2 that is kinda an MVC framework. This framework does not use any abstraction for the data persistence layer. So a typical model class would be like this:

class User extends Model {
    protected $iduser;
    protected $email;
    protected $password;
    // some getters, setters here

    public static getAllUsers(){
        // a select query here
        return $all_users;
    }

Now I think this model is using Object Relational Mapping (ORM), am I right? The problem is that it does not use any of the most popular patterns like Repository pattern or DAO for the communication with the database and all CRUD operations have to be implemented in each model. My question is if this logic is ok or it is not acceptable not to use any abstraction layer between the Model and the Database and why.