This is not selfish, but a kind of intellectual property protection. When you spend time and labor on this, other students may also be sorting out their extracurricular knowledge. It is natural for you and them to enjoy their intellectual achievements alone at this time. This has nothing to do with selfishness. More importantly, the object you want to provide is now your competitors. If you provide it selflessly, it is unfair to yourself.
When you graduate, you can provide it to anyone who needs it.