They don't. They do. It has.
And that's why.
But it's not a matter of welcome (or validation, or credibility, or, or, or) so much as it is to avoid confusion and distractions. Almost everyone (almost!) is well-intentioned, so it isn't necessarily a moderation issue, either. At least until the misunderstandings and disagreements get to the point of conflict. The simple fact is that there are limits to understanding, the applicability of advice, and the relevance of commentary, despite a high level of emphathy.