I think you are misssing the economics of the situation, which the GP is implicitly referring to. You have 24 hours in a day. A person that is making a web game that he wants to release cannot spend all of his effort chasing one in a million bugs, as that would eat into the time he has to actually make a great and engaging game. He can’t worry about how the game renders on Internet Explorers running in PowerPC. If you are making a kernel, a single RCE in an edge case (worse, even in a adversarially induced edge case) can equate to an emergency patch and general loss of trust in your system. The kernel programmer is even incentivized to do the opposite of the web game guy, which is remove functionality that they do not think they can reasonably completely test. So yes, edge case importance matters differently in different applications.