I can't speak for everyone, but they don't indicate my level of activity. A quick look at my post history reveals that prior to two posts in May of this year, the last time I posted was November 2012. During that period I did a fair amount of work on a bunch of different systems.
Generally, unless I'm giving a periodic update on progress or have a specific query for someone, I don't have much to post about here. That seems to be the case for a number of people.
I also suspect you can measure activity in different ways. If I'm renaming large quantities of files, I might post more often. At the moment, I'm working through the archives of the Atari 2600 Stella mailing list, collecting and identifying homebrew software posted there. This is lengthy and fairly painstaking work, yielding maybe 10 files per month of the archives - there's just not that much to say at the moment.