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I'm going to agree with Grace here. First let's look at our Area 51 definition:
Musical Practice and Performance
Beta Q&A site for musicians, students, and enthusiasts. Topics include practice & performance, composition, technique, theory, and history.
Obviously that puts the focus squarely on the art of creating music. History is really the only grey area — if we allow questions about the great composers of the past, do those questions have to be related to their music? And to what degree?
I think we've largely agreed that the focus of all questions here should be music or its production. For example, legal issues are off-topic. Despite clearly being relevant to musicians and consumers of music, these questions are off-topic because the focus is on law, ehich that happens to be related to music. The converse (music related to law) would clearly be on-topic, though I doubt there is much music written about law :P
For example, consider the generic question "Can I legally download copyrighted X without permission or payment?" Whether X is "music" or "games" or something else, the answer doesn't really change, and it requires legal expertise — not musical expertise — to answer. Conversely, "Will X help my guitar playing? Why?" is about playing guitar no matter what X is. Questions like that require musical expertise to answer and are what we're looking for on this site.
Now let's form the generic version of your question:
Do people who learn X of any kind like to show it to others?
To answer this question, the knowledge you need is simply the number X-learners who like to show their skills to others (statistics). This information would be created via a psychological study, since "well I know a few X-learners and I would say sort of" is not a good answer. Nowhere is expertise on learning X required; no matter what X is, the question can be answered perfectly well by anyone with the information, and that person is most likely to be a statistician or a psychologist.
If you were to ask it on a statistics or psychology StackExchange site, however, I believe it would be closed for other reasons. There appears to be no real rationale for the question beyond curiosity; SE's FAQ says questions must be about actual, practical problems. Second, the answer to your question is "Some people sometimes". There are a vast number of musicians in the world, with all sorts of situations and backgrounds. Some will love performing, some will hate it; some will take the attention for granted and not improve, others will be inspired, others will retreat from it. I'm not sure specific numbers would be any more useful.