Strava's only partially to blame. I put the rest on Facebook. Back when I first started riding in '04, club rides would at best perhaps average around 18-19mph for the 'fast' ride, and now, it's rare for us to average less than 21mph, and we often do 19-20 on even the 'hilly' rides. Facebook has helped this along by making everyone in the community patently aware of everyone else they know and their fitness levels, and not just by following them on Strava. The constant egging on via FB posts, ride invites, small elite groups of Cat3-ish riders and other neo-pro types who like to decimate slower riders to feel good about themselves. 5 years ago there was really just bike club rides, and now there are large amounts of various training rides and groups each week putting in some serious riding.
And that being said..... Bike clubs are falling apart, because people aren't showing up to the rides anymore. It's like this; "Hey man I see the club ride has a hilly 50miler tomorrow". "Nah dude, come to my house in the morning. Gonna be a bunch of racers there, and we're gonna drive an hour down to the mountains and put in a 70miler hammerfest over Mount St Helens and then go drink beer after". "Sweet! I'm in. I wouldn't want to ride with those slow club fuckers anyway". For this reason, I too also don't tend to show up to the club rides. Nobody's there anymore. Used to be, there's a huge variety of riders present, some fast, some slow, some new guys who get introduced to the faster dudes, and now there's none of that. New riders are often scared off by the uber-fast pace of the faster group, so they don't even try. The few I see show up on the scene now that survive are ones who are often friends of a faster dude.
What makes matters worse on FB too, there's always that gaggle of guys you know who either don't work, or don't seem to have jobs that tick you off. They think nothing about taking 2-3 days off and doing some mountain tour bike riding, or racing back to back weekends out of state, or just putting in a 90 mile solo ride on a Tuesday, well on their way to a 400 mile week of riding. Ugh. And they post this stuff all over FB...
Seems also like everybody, as Nate has said, has to be racing or training for one to be considered acceptable in the community. The pressure I get (as a faster rider) to enter crits, road races, etc, and just show up for some massive hammerfests is immense, and I very often just don't have the stomach for it. I rarely encounter guys who are somewhere in the middle on fitness or who don't race. Seems like it's always a bunch of either complete newbies (who will be a Cat3 in 6 months), or guys who are.... Cat3s. I shit you not though, there's this one group of riders near me who would each be a very strong Cat3 rider....but they don't even race!! It's like, dude, WTF are you pushing this pace so hard...
I am convinced that more than a few of these people are taking various doping products btw.
Ever since I've taken up cycling, I've liked to ride fast, but as far as 'training' for something, I might devote about a month or two towards it. I just lose interest after that time, as the constant bike riding, prep and other things just start to bore me. I LOVE cycling, but if I make it all I'm about, period, then I would lose interest. Cycling has to have an appeal to me (something I'm not doing but might want to do) for me to keep the interest, so I have natural highs and lows that I go through with regard to riding and doing events or races. This time last year I was perhaps to be considered a 'fast' Cat3 in fitness, and things were looking strong, but I just got tired of constantly heading out for a ride. Loved the fitness level I had, and how lean I was, but it's a serious amount of work, and the last thing I want is a 2nd job.