[fat_cantor]

It's an American thing, which traces to Bill Clinton's development of the factory farming industry when he was governor of Arkansas. The good old-fashioned eggs and chickens are still widely available at farmers markets, etc., but presumably not used for testing here. The point about cayenne being the only chile-based heat also depends on region - Cajuns, Creoles and New Mexicans would likely disagree. Edit: another factor is probably the dramatic decrease in the population of insects since 1970, which affects the composition of both the chicken and the egg