I think what happened was starbucks found the market for "trendy" drinks and cups: unicorn frap, color changing cups, tie die frap, black studded cups, (and many more). People are into them because they are great for social media (and some taste/look good). The hype exaggerates the desire for them. Then when people start buying out entire stores to resell them online, it only wants to make people buying more.

I hate it so much, but it makes for great business