https://www.musical-u.com/learn/musicality-means-sight-reading/
Learning how to sight read well is a key to good musicianship
Musicians run into sight reading in a number of situations, from filling in for a missing player in a live performance, to recording studio scenarios, to music exams.
Once you have mastered the skill of sight reading you will be able to play your heart out like a pro even if you’ve never seen the music before.