Problem is a simple camera solution wouldn't work, there was one on the goal line here and Bowen's body was in the way. It would need to be something with multiple cameras like GLT, and Hawk-Eye is said to cost around £250,000 per ground. That makes it around £1 million a decision over the course of a season, no idea if they could reduce this by using the existing cameras but I doubt it as they are pointed directly at the goal.
Granted that is small fry given the EPL's wealth, but I can't see it being high up priority lists. Plus where do you draw the line, do you also need cameras to check whether the ball went out for a throw-in prior to a goal?