Why lime wedge in Mexican (Corona) beer?

Many have the opinions that it is unique to the way of consuming this popular brand of Mexican beer. Incidentally, this practice is uncommon among the locals in its native Mexico. Rather, it is usually seen among the tourists there, and in the export markets.

Plausible background behind the practice of inserting the lime wedge into the bottle neck range from it being a cleaner of rust stains around the bottle mouth (due to an early practice of metal caps without the rubber liner/seal); to it being used to keep the flies away (probably by the early tourist drinkers).

Another contender for the inspiration of the practice could perhaps be the Michelada, a popular beer cocktail made with the addition of lime juice and hot sauces. Though in this light, perhaps Corona with a lime wedge might actually be considered a sort of semi-cocktail?