> It prohibits the URL owners from changing it.
That's mostly about the social contract: if you publish something on the Internet, should it be made easier for the readers/users to access, or for you to move the thing around for whatever silly reason?
> I let the URL owners to have freedom to change it.
You know, you used the term "URL owners" twice, and I think I have a fundamental problem with this concept. The publisher ought not to own the URL, it really ought to belong to the consumers.
> A thing that changes or goes away, feels natural.
Yeah, but the URL is not a thing of nature, it's manufactured, and its original intent was that it was manufactured to last.
> An URL that didn't change in 20 years, actually freaks me out, like a non-degradable plastic.
A URL that doesn't change shares zero problems that non-biodegradable plastic has. In fact, the constantly changing URLs do have a couple of problems similar.
Also, you can try a different metaphor, like e.g. a rock or a mountain. It's a freaky thing, innit? Always there, unchanging... until people with excavators show up and turn a mountain into a quarry (which happened to several mountains, actually). Take it, nature!