Why isn't it a requirement that all shelters and veterinary clinics use the same microchips and read

Why isn't it a requirement that all shelters and veterinary clinics use the same microchips and readers? Or, if there are different frequencies of microchips and each requires a separate scanner, why aren't they required to have one of each scanner so microchips are never missed?

A:  There is no federal or state regulation of microchip standards in the U.S., and different manufacturers are able to produce and patent different microchip technologies with different frequencies. Because of market competition, animal shelters and veterinary clinics are able to choose from several microchip manufacturers and scanners. Microchip scanners are relatively expensive, and it is often cost prohibitive keep one or more of each type of microchip scanner.

This problem can be solved by the use of universal microchip scanners, which are readily available. The use of ISO standard microchips would be a good step in developing a consistent microchipping system in the U.S.