I did find this bit interesting too...
> Apart from this practical reason, there's a principal one: The first time I invoked Netscape, it said that it is obsolete and refuses to work. I don't use software that thinks it knows better than I when I should stop using it.
...considering the modern trend for autoupdating software. The author (after this paragraph) also considers availability, but another issue is if the software is something one would like to use even if it is available - for instance, personally i never liked using a version of Paint Shop Pro after version 7 since i found all of them a degradation. I can use PSP7 just fine though (even on Linux via Wine) - imagine if the software decided by itself that it is too old to run or to replace itself with a new version against my wishes (this is something a lot of software does nowadays).
From a user's perspective this also has implications on preserving backwards compatibility for foundational functionality programs rely on.
[0] https://people.inf.ethz.ch/wirth/Articles/LeanSoftware.pdf