Earlier quoted context omitted.
Trail on road bikes, racing and not, seems to be universally in the range of 55-60mm (across frame sizes, too). I suppose it depends on what kind of racing you're doing, but some kinds of bicycle racing involve cornering agility / nimbleness, and you want a shorter trail for that.
Randonneur bikes (also road but with fatter 650Bx42 tires) typically have longer trail (typically in the seventies) because they carry front loads.
SeanLuke provides a good example with the caster. I also recommend reading Dave Molton’s blog (who’s built frames longer than most people here have been writing bloated JS SPAs) for more:
Trail, fork rake, and a little bit of history - https://davesbikeblog.blogspot.com/2007/05/trail-fork-rake-a...
Now porteur bikes and typical randonneuring bikes often have lower trail. People are often focused on the trail numbers, but the simple reason is to position the front load (handlebar bag or stack of newspapers) on or right behind the front axle. Framebuilders do this by increasing the rake (fork offset) to stretch out the front axle, which results in decreased trail. The reason is that you want the weight at the fulcrum to reduce any "inertia" when steering--so the bike remains easy to steer with the additional weight.
If you’re not intending on riding your bike with a front load most of the time, then you probably do not want a low trail bike as they are more sensitive to rider input on the handlebars when there is no weight. Also, randonneuring is just an activity, so you can ride any bike with any geometry you want. But in America, especially on the West Coast, there is a bit of bike-cosplay in the randonnerding scene, so folks like to ride bikes built in the old French Constructeur style.
Lastly, SeanLuke is probably not familiar with mountain bikes, but modern geometry for XC and enduro bikes is towards slacker headtube angles (resulting in higher trail) for stability when descending.
For anyone interested in geometry, I highly recommend browsing Bike Insight's category section: https://bikeinsights.com/categories