- Edited
There are online discussions whether kids learn better or faster than adults. The simple answer is NO. We learn differently.
I come from a non-musical family. Everybody in the family had music lessons in the past including recorder, violin, guitar or accordion but nobody played at a high level or became a professional. A few months ago there was a performance of the Tchaikovsky "Pathetique" Symphony #6 on TV. Mom watched the performance without any emotional response. She didn't know what the music was all about besides the fact that it has 4 movements.
As an adult learner, I don't have a choice to start earlier. Growing up dad had a collection of Classical LPs. There was always music in the background but nobody was drawn to any particular instrument. A few cousins took lessons including flute & violin but nobody would talk about practicing or playing songs in the past. The peer pressure to get into music wasn't there. People would say we get further starting before 10. I wasn't ready until a few decades later. I got into music as a hobby than even passing conservatory exams. The main reason I got into piano was stress relief from work and other issues in life. I'm not concerned with research data or statistics on the ideal age for starting piano. I play keyboard at least an hour a day like taking my vitamins & antidepressants.
Parents getting kids into piano or violin at a young age are giving them the gift of music. On the other hand, kids know next to nothing about "Classical" music or the instrument they're supposed to learn. There is a bit of trial & error to see if they're interested in playing an instrument and whether piano or something else is the right fit. The majority of students don't end up becoming profession concert pianists or musicians. Years ago a friend brought her 2 sons who were in Suzuki piano & violin along and played a few pieces for us as duet including "Minuet in G". They were asked to play at their grandfather's funeral in church. After graduation neither became professional musicians.