The reason is that modern people study calligraphy as an art, and not everyone studies it. Learning calligraphy is just a hobby and has nothing to do with one's occupation. At the same time, modern people have too much to learn to confine themselves to calligraphy.
The ancients were different. The quality of calligraphy was related to the future of scholars. Even if they can't be "home", the calligraphy level of ordinary scholars is much higher than that of modern people.
Compared with the ancients, modern people also have very good calligraphy works, but the overall level can not be compared with their predecessors.