[nuancebydefault]

I find this hard to believe.

> cd command implementation does not change.

I'm pretty sure the cd implementation needs to interface with different file systems. Those interfaces change or at least new interfaces appear when new file systems emerge.

> The word processor does exactly what it needs to.

What we use a word processor for, changes over time. Does the print function still work for my inkjet printer, in A4 format? Can I write emails with it, why should I even use the word processor if my email client has an embedded word processor? Can I embed images, only TIFF maybe?

Unfortunately there is no such thing as forever software, unless you don't change the circumstances in which it is used, which is very unlikely.