I played on the piano for the first time when I was 9, 10, and 11, and quit, because I felt too overwhelmed at the difficulty. Only recently, about 3 weeks ago, I decided to return to the piano again. I have many reasons why I want to play the piano.
1. Cognition. I want the piano-playing to help me become more aware of the environment and process things more efficiently and quickly.
2. Hand-Eye Coordination and Dexterity. I want the piano-playing to improve my hand-eye coordination and dexterity. As I progress through music sheets, I notice that I have to do octave stretches, finger crosses and jumps, and figure out the best finger placement to play the desired notes. The more I practice, the better of a sight-reader I become. Brahm's lullaby requires some hand movements in addition to finger movements (so it may be helpful to know how to play just by sight-reading and without looking at the hands).
3. Singing. I love to sing, and I just want my piano playing to help me become a better singer.
4. Entertainment. For me, I find that piano playing is a productive form of entertainment. I have seen one homeless guy on YouTube who has a music background and makes tips on the streets, playing piano. When I saw that, I was like, "Sounds like a good idea." If I play an impressive performance, then I may earn some tips as a side income.
I know all the major scales now; before, I only knew the C major scale and the CEG chord, and somehow those two were the only ones that persisted in my brain in 15 years. In 3 weeks time, I can play 13 different musical pieces, most of which are beginner-level. Most of the music sheets fit into the classical, Christian, or children genre. You may be surprised at the number of people who ask online whether it's too late to play the piano. Personally, I believe that it is never too late. You can start at any time. In fact, learning as an adult is actually much faster than learning as a child. In my personal experience, a simple musical piece like "Are you sleeping? Are you sleeping? Brother John. Brother John" takes just about a couple of minutes to learn and play with both hands simultaneously (right hand melody, left hand harmony), provided that you can already read sheet music and have performed more difficult pieces.
I long for a day where I can find an audience other than my parents. Maybe someday I may casually play an impressive performance on a street piano and earn tips. In the meantime, I'll just have to keep on practicing. Practice makes perfect.