The necessity for reading music depends entirely on what one wants/needs to be able to do.
Reading music at a high level generally takes years of study, particularly for piano.
Depends also on the instrument one plays; there're tabs for guitar, treble and bass clefs for piano, treble or bass clef for wind, brass and string instruments, lead sheets and chord charts for guitar or piano, full score for orchestras..... Different kinds of music reading exist.
For most genres, a lead sheet or tabs are enough. And some musicians just use their ears, and sometimes that can be enough too. Except when one has to play a song one has never heard before.
Yeah, it really depends on a lot of things....