why do we never hear of 7 year old bands then? i think there's more to music than just technique and vast majority appreciate the artistic aspect. but i can imagine musicians appreciating the technique.

Most, if not all, musicians in any professional symphony orchestra was at one point an unusually talented 7yo.

It just takes many years worth of practice to get from being good by 7 years old standards to being good enough that people buy tickets to see your performance, especially in the classical music culture where skill, or "virtuoso", is everything.

Did you watch the video? Her expressivity and musicianship is far beyond many adults.. She had also just finished a concerto playing with an orchestra

EDIT Also with band music or non-classical music so much of it is to do with platform and distribution, and 7 year old prodigies don't get much interest outside of talent shows or Youtube. Justin Bieber (as mentioned in another reply) though is a good example of someone who did at age 12

Are you looking for facts that will contradict your opinion?

Justin Bieber clearly was that. His youtube videos got him discovered at age 13-14.

Vanessa Paradis made her first public appearance as a singer at age 7.

There are several children prodigies I've seen on YouTube (singers, drummers, guitarists). They clearly have such talent that even at young age they do music better than most people would do with infinite amount of practice.

As to your question, the prodigy is, by definition, extremely rare. They clearly exist (Bieber, Paradis) but, by definition, you can't expect to have a lot of them.

And "why aren't 7 year olds headlining for Taylor Swift" is not a fair bar.

There are reasons 7 year olds don't do world wide tours that have to do with things other than musical talent. Like being in school or not being allowed to take a bus by themselves.

Classical music and popular music are two completely different fields, and there is almost no way to evaluate them interchangeably.

Michael Jackson is another. And there were child stars in the movies.

One difference is how popular music is produced today. The members of the band are not just performers, and in fact, they're often mediocre instrumentalists and singers. They're expected to create their own material, which probably requires a certain level of social development and experience. The emphasis is on other skills such as creating songs that resonate with the audience, performing on stage, etc.