People on the hike
How far you had to drive to the trailhead
Negative situations: Someone got hurt etc.
These factors are unique to that hike and no one else will have the same experience as you did.
As an example: Let's say during a hike you meet someone and he or she offers you a dream job. You would rate the hike as one of the best, even though the actual route might be boring.
Rating a route is much different. You are only rating the quality of the route, which normally does not change. True it's a subjective rating, but most things are in life. Since the route is the same, every hiker experiences the same route. There are no other factors to consider. Thus when you rate a route it gives meaningful feedback to other hikers who have not done the route.
Let me know if you agree.
Join the best hiking club in the southwest: http://www.meetup.com/Hiking-Las-Vegas/