That question has been put and the response was "we get enough applicants". "Never mind the quality feel the width" comes to mind.
It costs several $100,000 to train a controller & they worry about a few $1000 here or there. You could up the trainee pay by say $20,000 and come out ahead because you'd attract a higher quality of trainee. One extra pass every couple of courses and you'd be in the black.