I can't go very fast even on my (small/cheap) ebike and have definitely noticed (even with not-the-best-eyesight) plants/animals, flooding, nearby infrastructure/locations, smells etc. on the trail. I wouldn't say 15kmh is "barreling" and is my average comfortable speed. Slowing down or stopping to walking around a bit is also incredibly easy (and a thing already you stop to rest/drink/eat anyways), but you can still make up for lost time if needed.
In the context of a show, I could see a lot of angles to this. From somebody remembering something they briefly saw to 1 person in a group investigating something (staying behind, rushing ahead, taking a sample etc), also successfully evading chases and camp-y rock ambushes.
Personally I'd also say that biking long distances just seems easier than walking/hiking. Maybe mechanical advantage (esp. w/derailleur) or the speed, maybe health issues, or maybe there's just something about the feel of it that's boring/taxing to me. I can't imagine walking 20 km but is something I've done a few times on my weak ebike.