Why should anybody pay for anything related to Eloquent if there exists something free of charge related to Doctrine, that is the first thing.
The second, ORM as an idea converts into a resource consuming and over-engineered overkill in case of evolution of your domain into more and more sophisticated structure making serving queries construction complex and inefficient comparing to dbal served by string queries created by simple query builders.
ORM query builders presents themselves very nice in case of primitive CRUD examples presented by tutorials. In real life, and coding, when serving your domain requires much more than a simple CRUD, ORM is noting but an obstacle.