Why are dwarves so popular nowadays and not midgits?

Dwarves and midgits suffer from two different congenital conditions. Dwarves have what's known as 'achondroplasia', a condition that results in unusually short arms and legs and mild facial deformities. Midgits, OTOH, are well-formed people who are much smaller than normal due to a hormonal malfunction. The two categories have little, if anything, in common. Back in the 1930s when "The Wizard Of Oz" was made they had no problem with finding dozens of midgets (and dwarves) to play the Munchkins. These days there's even a cable TV show, "Little People, Big World", devoted to dwarves. Every time I see a "little person" (a derogatory term if ever I heard one!) on TV it turns out to be a dwarf, not a true midgit. So what happened to all the midgits? Are they all hiding, perhaps trying to fit in as normal people? Or has medical science advanced so much that hormonal abnormalities can now be detected and fixed prenatally? Or have there always been many more dwarves than midgits? This is something I've not seen discussed anywhere. What's the deal here?