Impactful Writing
R' Moshe Feinstein19 writes that if a person has the opportunity to publish his Torah insights but chooses not to, he has not fully fulfilled the mitzvah of teaching Torah.
He compares it to someone who has the ability to teach 100 students but decides to teach only 50. By publishing one's Torah, besides the fact that he preserves his Torah for himself that he may otherwise forget, its influence can extend far beyond the walls of the beis midrash, reaching countless people for generations to come, even after he passes away. People who would never have the opportunity to learn from him in person can now be impacted by his Torah.