Well, it's a good idea.
Many piano students are usually learning in old pianos, not well maintained, out of tune.
Some schools are investing on digital pianos.
For piano beginner it's welcome learn even in a sampled piano, as it's always in tune, since a out tune piano tends to miss train the ears, and people who got used to out tune may tends to strange a tuned piano.
The probleme comes more ahead, when music become more complex and the limitations of most sampled pianos become a problem. You can't expect a student of the technical level , to be pleased with average sampled piano.
Like said pianist Hugh Sung: "I always hated, really hated to play in digital pianos, until find pianoteq." For hin the lack of variances on pianissimo and progressive slow rising of velocity was always a anoying problem in sampled pianos.
Also most schools couldn't pay for a expensive top CPU computer to run the last modern giant (space required) piano sampled libraries.