Comment by whiteboardr

I think there is a big difference in physically working towards the speeds you mention and just rotating a grip to move (fast).

Having to work for high speeds, even if just rolling down a long hill on a “bare” machine, regardless of material or price, will create a much deeper mental involvement of what you got yourself into.

Thus, unassisted cyclists are (my guess and own experience) much more aware of their surroundings, what lies ahead and thus alert.

Things obviously can go wrong either way…