Because Math requires greater knowledge. Damn near anybody can be an English teacher, not everybody can be a Mathematics and Physics teacher.
Calculus, Calculus 2, Calculus 3, Differential Equations, Thermal Fluids. shyt ain't no joke and a lot of people will get bodied. Most drop that 2nd year
But they're better in the long run and pay off. More Math/Physics = Bigger pay check + More Job opportunities. Meanwhile the English teacher making $45k/year and competing with way more teachers.