Cost of HT.

[Flyndaran]

Originally Posted by Nereidalbel

They're also at a higher TL. What our first-year college students learn today would have been reserved for the most gifted of students 400 years ago, after all.

You can't cram calculus into a normal 12 year old head no matter how amazing your teaching techniques.
One difference is that moderns are more likely to allow specializations rather than push hard for "Renaissance men". Math prodigies, for example, can let other subjects lag to attain higher ability with math alone.