[Archaea]

but these are big crossings, more than several hundred yards each.

It probably got started that way and never changed. One thing which perplexes me about "rides" as opposed to triathlons and sometimes races is the lack of support. In a cycling race, you provide your own support. In a ride, they have the support off to the side, but it takes so long, you lose too much time. In a triathlon, the support is road side and doesn't really require stopping, just slowing down. It wouldn't take much to just hand off water or other drinks, as they do in triathlons.