Why do we teach our kids games? Is it so they become especially good at playing chess? or poker? or bridge? Are we hoping that they'll go pro? I think your comment misses my point. We prepare our kids for life. Not just for a job. And life involves all kinds of skills.
I didn't say "only ever doing one thing and doing it well is good for a person". Learning multiple games is also good; learning many things is also good, my (trite) point is that IMO there is a specific virtue in the pursuit of excellence: the stripping away of imperfections, the alterations to one's temperament required to reach excellence and then to demonstrate it, the self-knowledge of what it takes and that one has it and could demonstrate it again, pure self-esteem, etc.
