Probably because the factories have been told to "push" the manufacturing of the current waves as a higher priority than refilling older orders of previous product.
At least the distribution of the blind bags really does make it a bit of a hunt for the little collectibles, doesn't it? Finally having them in your hands gives you a great feeling when you achieve them at last!
At least Wave 3 will actually retain some value behind it in later years if it's the most-poorly distributed wave of blindbags. Just makes it a little challenging right
now.
Hopefully BBTS has a reasonable pre-order policy if the manufacturers don't follow through.