I know why they are called “dead-ends.”
But that is not what I’m interested in.
The way we use the idiom makes it feel like a full-stop “NO.” But, aren’t dead-ends simply a “no” that leads to a different “yes”? Maybe the theory you were banking on was wrong, but the “no” to that theory is valuable information that leads to the next one. Maybe it’s a no to that job you wanted, but a yes to something else. The list goes on.
It’s not the end, it’s simply the beginning of something else.