Whatever scale one uses to evaluate sites, there are good reasons to do so or at least have some familiarity with what these mean:
- Determining whether or not it might be worthwhile to explore some other sites with a scope (whether near or far.)
- Being able to decide what sort of targets one will likely be able to see, find impossible, or find very challenging from a given site.
- Being able to understand what sort of conditions allowed another to observe something...or not observe something.
- To be able to help guide others when they have questions about why they can't see something at their location or whether they might expect to be able to do so.
Just being aware of the sort of things to look for at given levels is rewarding, because it is fundamentally visual observing. This is true whether one is a novice or a veteran observer.
The more you see things in dark sky, the better you can become at finding them in somewhat brighter sky when conditions are favorable. While in a discussion with an astronomy professor/researcher the topic of the gegenschein came up. He said he had only seen it from the pristine skies of the Kalahari. He was surprised when I told him that it was often visible from our local, low elevation star party site, nominally Bortle 3. And on the better nights I can trace the zodiacal band from it as well. A few years ago I would not have noticed it, but since then I have had far more time in Bortle 1 & 2 conditions and that has made me more familiar with the phenomenon and where to look for it. There are many other naked eye objects that I did not realize were visible years ago.