Personal attention is very important in education. Video games generally lack the personal touch that helps promote learning and retention in students.
Video games may sometimes lack the depth of traditional kinds of teaching. It is difficult for those learning using video games to get additional help or be able to ask questions.
Video games generally do not help promote the same attachment with learning in the way that traditional learning would. It is not uncommon for students to only see educational games as just "games" without giving attention to the learning potential.
When students make use of both educational video games and non-educational video games, they sometimes develop a difficulty in distinguishing play from work. This can cut down on the ability to manage time well between work-time and leisure-time.
Educational video games can tend to be relatively expensive. An attentive teacher will almost always be more cost-efficient than an educational video game.