Hi Paul!
I went to FSCONS a whole five years ago and met quite a few FSFE people, but I think it hasn't been as popular amongst FSFE people in recent years.
2007-2012 or so, it was organised by me and a few other FSFE people, which naturally contributed to its popularity then amongst the FSFE crowd. We typically had quite a lot of speakers from the FSFE community as well which contributed to making FSCONS almost an FSFE conference.
The FSFE also had a booth there one or two years ago, but there's another team in charge of the conference these days and so it's less of an FSFE event. :-)