I've actually cycled a little less since retiring in Nov. of 2007, but it's pretty much by choice. I'm writing for a couple of publications (I was a newspaper reporter for 30+ years) and doing a radio show. I ride enough to stay in reasonable shape, and probably will pick up the pace as the weather warms with an eye to doing a few longer rides, possibly a century, in late summer.
The point is, though, that you have a choice. If you're retired and want to ride more, all you have to do is get on the bike.