Not enough profit when they can chase other, more profitable avenues.
My statement is that good customer research kills bad ideas before they hit the market (so you don't see the failure). However, it can also be the case that it won't spot a good opportunity, therefore there is no product in the market to succeed or fail.
Basically, your statement of there not being a case of a product failing does not prove that market exists. It also doesn't prove that there's no evidence that the market doesn't exist. It just means that there's no publicly available evidence that the market does or does not exist.