You do have an (optional) minor version number which you increment, you just call it a build date and don’t make it part of the version number or part of the filename.
This means I have to remember not only what version of EE I use but when I last downloaded it. How is this easier than incrementing the final part of a version number?
To me a product has different versions when different downloads have different contents. The filename should reflect the version so that downloads of different versions can exist in parallel and be distinguished.
Otherwise e.g. some download managers will tell you you already have the file when you try to download it despite it being a different file with different contents or worse will overwrite a known working version by a new untried version without warning.
My preference is for 2.1.0, 2.1.1 etc. Using 2.1.0-20100810 is equivalent but more difficult to read at a glance.
What I need in summary is for some way in which multiple downloaded versions can coexist without any renaming effort by myself. I also want a instant way to tell if the version I have is current or not. For me the current scheme fails on both points.