You can also get an ‘Aerial view’ that would allow you to spot patterns and such. When reading you can basically instantly get to any point you want. Jumping along to similar passages based on similarity is slow. And repeating sections can only happen at the pace of the playback. If you miss something you have to manually use whatever interface to seek the point you missed. Using any non written prerecorded format for learning music severely slows you down. Time - the biggest most significant disadvantage. Jazz players generally know how to follow a lead sheet etc. Guitar players generally know how to follow a song by ear. By learning standard notation and conventional methods for you chosen genre and instrument you develop the ability to get started with others with relative ease. You’ll be limited in what you can play with other musicians or even strangers. You might be but assuming you rely on this format only I doubt you’ll be doing many scales and études You aren’t necessarily exposing yourself to technique building exercises. Also there would probably be only one or two arrangements of the song. While you think just about any song is there I am willing to bet that that’s not true. You can only learn pieces that somebody bothers to prepare for YouTube. What ever other reasons you can think of for why you do it now. You get to hear the song while you go along You don’t have to learn standard notation now

Just like learning guitar music with tabs rather than traditional notation there are advantages and disadvantages. Whether it is the best idea or not in the long term depends on your goals.

Make synthesia songs