Miscellaneous Musing #64

The USA's "national" anthem is not played when places of business or schools or even government offices open for the day, or at the commencement of a musical or theatrical performance or even of a presidential address, or under almost any other non-athletic circumstance, and so why is it played at the beginning of sporting events?  Do the organizers of such events fear that, should the anthem not be played, the attendees might not know what country they're in?