I imagine you are asking why the grand architect included the second rule, as what it does seems clear enough.

The honest answer is I don't know. No one has explained it to me, and I wasn't there when it was born. But Debian being what it is, I'd be surprised there if there was a grand architect, or that it's possible to point to a definite moment in time it became a thing. The formality Debian has acquired over the years looks to be to attempts at codify existing practice after it was challenged. Codifying works to prevent reoccurrences of the unpleasantness associated with such challenges.

The practice has always been someone volunteers to maintain a package, they expected nothing but the freedom to do the job in the way they saw fit without fear of interference providing they followed policy, and no reward except the bouquets and bricbats for how it turned out. When put that way it's not much of a reward, but it's been enough to attract a lot of us to the task.

The importance of that reward can best be seen by looking at what selfish motivation is left if you took it away. Good deeds are great and all, but when done where nobody can see them or others can easily take over after you've put all the hard work in or worse can claim credit for it, such hidden deeds are not great motivation for sticking at it for years.

We are all very aware that binds us and we are protective of it. But human nature being what it is, it can't be surprising the second rule has been challenged on many occasions, which has lead to it being codified in so many ways it's become part of Debian's DNA.