Eating a dessert pie during or after a bike ride is a tradition that goes back decades in some parts of the USA. I've found references of Wisconsin cyclists partaking of this tradition going back into the 1960s. Don't know when it started.
The tradition is not exclusively a 50+ thing. Riders of all ages participated. It was also not an annual event, it was an option on every ride, but more frequently it was weekend rides.
In both Wisconsin and Minnesota there are bakeries and pie shops that have been located on popular bike trails specifically to cater to the biking community. Several communities, in the Midwest and in other regions, sponsor annual Pie Ride events. Here's a link to a page about a cycling club in Clinton, Iowa that organized around pie rides in the mid-70s:
http://www.rbbcclinton.org/history.html
I've seen references to pie rides in Massachusetts, Texas, Oregon, Montana, and other states.
I believe a Wisconsin member of this forum, rck, was instrumental in bringing the tradition to the 50+ BF forum. He or DnvrFox can supply details.