alt Hacker NewsOkay, a scenario where you're building a hobby project alone and you don't care if or when it gets finished would be one where estimates aren't needed.
There is no scenario where it's appropriate or necessary when developing software professionally or even as a side project where others are expecting you to complete work at some point.
One of the many misconceptions in the original comment in this thread is that "worthwhile software is usually novel", which is not the case without a very specific and novel definition of worthwhile that I don't believe was intended.
If software isn't novel, that means some other, existing software does the same thing just as well in the same way on the same platform. So, unless it's a hobby project you're building alone, why don't you just use the existing software?
I think that writing software that isn't novel fails to be worthwhile by a perfectly ordinary, mainstream definition of "worthwhile".