On that note, Zawinski's Law:

“Every program attempts to expand until it can read mail. Those programs which cannot so expand are replaced by ones which can.”

This is mostly true, but it does not have to be. :(

  "Software is never rewritten. Projects last longer than expected; programmers get bored or burned out; management moves on the newer challenges. The attitude of ‘good enough’ reflects reality.

  Instead of being rewritten, software has features added. And becomes more complex. So complex that no one dares change it, or improve it, for fear of unintended consequences. But adding to it seems relatively safe. We need dedicated programmers who commit their careers to single applications. Rewriting them over and over until they’re perfect. Such people will never exist. The world is too full of more interesting things to do.

  The only hope is to abandon complex software. Embrace simple. Forget backward compatibility." - Chuck Moore

Software in practice needs to run to classify. Without that it's just a .txt file that won't compile.

Otherwise you're talking about a standard, a protocol, a document with no program. Instructions for humans how to program computers.

that is just false. I've seen plenty of one-use software - made specifically for trade shows, exhibitions, etc. which were never reused again because the entire software was the logic specific to that particuliar exhibition.

there is also a few thousand gigabytes of old game ROMs and abandonware on the internet which are all perfectly done software.