There may be zoning restrictions on where these shops can be relative to schools, daycares, etc. that prevent them from opening in good locations. This also ties into your third question.
Social stigma, lack of expertise about the product among the people with the best means to open a new business, uncertainty about a new market with no prior data to base expectations off of. Someone with good credit, capital to jump start the business, and the kind of prior business experience that would be helpful might have trepidation against jumping into a new market like this.