Years ago I found out that there is a parenting video floating around which states that children who play sports go to practice, then come home, and even though no one tells them to practice, they go find a ball and kick it around, yet with music they are told to practice. The video then asks "why is music different?" with the clear implication that we should not expect music students to practice unless they decide they want to, and possibly that if they don't want to practice they don't like music.
This sort of thing is the bane of my existence.
There are a few important distinctions between group sports and private music lessons, the first being that most sports practices run multiple times per week and/or are several hours long.
By contrast, private music lessons (at least at the beginning) are half an hour once a week. That just isn’t enough time to master the skills required to play an instrument and be able to make progress.
There are a few programs that run group lessons several afternoons per week for several hours, similar to group sports, and if you are doing one of those, it’s true that you can probably get away without doing home practice and still see progress, because you are putting in hours on the instrument during class.
However, another important distinction is that by the time you enroll your child in soccer, for example, they already know how to run and kick a ball while a new beginner learning a musical instrument is introduced to very intricate fine motor skills in a manner they haven’t been exposed to anywhere else, and this process is more the equivalent of the toddler stage of development where a child is learning things like walking/running and ball-kicking, rather than the stage where they have mastered these skills and are ready to do it in a team setting.
Now, addressing the fact that children will just go find a ball and kick it around without being told. One of the things that can make that attractive to a child is that it can often turn into a social activity, and, if a child has a friend who plays an instrument, then yes, they do often voluntarily play together once they’ve reached a stage where that is possible. When I was a teen-ager, I often took my violin to my boyfriend's house to play duets, I have students who play recreationally with their friends, and one just took it upon herself to make a string quartet arrangement of a song she likes. I have also heard from collogues about their students who take instruments on playdates unprompted. You have to reach a certain point in proficiency for this to be possible however, and that requires practice.
Most children don’t have a neighborhood full of other kids who play instruments though, so it’s an unfair comparison between ball kicking and music playing and if a child is not voluntarily playing music with friends, or not doing it yet, you also have to consider the cultural and parental attitude towards the different activities. Kids will pick up on these even if neither you nor they are consciously aware of it. We, as a culture, celebrate sports. Sports are everywhere. We watch sports on TV, we have favorite sports teams, we have favorite athletes, and we talk about our favorite teams and athletes constantly. Then we drive our children to their sports practice and sit there watching them and cheering them on through every game.
We mostly don’t do these things for music. Most of us don't have favorite orchestras, or classical soloists we talk about constantly. Parents don’t watch children practice at home and cheer them on. Even if there is parental supervision of practicing, the parent is most often correcting the child rather than encouraging them.
If there is one activity that gets you sent to a room away from the rest of your family, or potentially has a parent looking over your shoulder waiting for you to make a mistake, and another one where you get to feel like you have your own personal cheerleader, which activity would you associate with a more positive feeling? (Disclaimer: I realize that not all parents watch sports practices or go to every game, and some children get harshly criticized for their performance in sports which is awful. To keep this post a reasonable length I am dealing with generalities)
In many households televised sports will be regular viewing but it is unlikely that those households are also watching televised international music competitions, although they are there for the viewing.
Please know I am not saying you SHOULD do any of these things. I’m just pointing out that since we as a culture approach sports and music very differently we can’t really expect children to approach music the same way they approach sports, even if we want to humor the idea that the two activities are comparable.
Really though, the comparison between group sports and private music lessons is flawed, at best. You’d be getting closer by comparing group sports practices to youth orchestra rehearsals but even then there are issues. In both cases, the participants already know how to play and are practicing doing so in a coordinated way involving teamwork. With a musical instrument though, it’s virtually impossible that you’d be able to go into rehearsal and actually be able to play your part if you didn’t work on it at home, so even this comparison falls apart pretty quickly.
So, in closing, both sports and music have some wonderful benefits, but comparing the two is problematic. Celebrate both for the unique activities they are and know that just because you (or a child) likes something doesn't mean they will be excited to do it 24/7.