The list of reported versions on one of my sites is 45 lines long! This is because the user agent pepper differentiates every minor version change of Firefox:
18.104.22.168, 22.214.171.124 … 126.96.36.199
Most people don’t need that many details. And since the entries are spread to so many versions, most of them count as “under 1%”. It’s hard to figure out how many Firefox version 1, 2 and 3 are in use and I guess this is the most important information regarding version numbers.
Or do others care about the exact version number?