Many people are content to read written music. They're good at reading music and they can sight read well. They don't have to think of what to play, they just play what's written. Being able to read music is a valuable skill just as reading what other people write is a valuable skill.
But some people struggle to read music--especially left hand notes. If you've ever had to practice a song for an event, you may have had trouble finding an arrangement that was easy enough to learn, yet advanced enough to sound impressive. Or you finally learned a four-page song except for two or three tricky measures that you could never play well.
One more drawback I have found to only reading music. You get "stuck on the page." I've had so many adults tell me that they took lessons for years, could play quite well, but couldn't play anything without music in front of them. When you learn chord piano, especially when you start working with the theory in my Chord Piano by Ear Workbook, you will learn what chords naturally work together, you'll be able to anticipate what chord to play next, you'll be able to memorize a chord progression much easier than a full arrangement and you'll eventually develop your ear to the point where you can play most of your favorite songs by ear.
You'll always be thankful that you are able to read music, just as you appreciate being able to read other people's words, but you will also be able to play more spontaneously and without sheet music!