Doesn't anyone believe in self-selection?
There are different types of runners. If a runner thrives on long runs (some do and some do not), that runner will likely "enjoy" the long run. That runner will also likely naturally gravitate towards the longer events, not only because a vast majority of his muscle fibers are Type I fibers, but also because a longer race will provide the best results given his endurance-oriented training.
If someone doesn't "enjoy" the long run (and keep in mind that the duration of "long" is relative), it is likely that he doesn't gain as much benefit from that type of run, meaning he likely isn't as endurance-oriented, which translates into likely enjoying/thriving on the shorter/mid-distance events. In this case, why run 2 hours? All cardiovascular activity falls on an aerobic continuum of duration vs. effort anyhow.
75 minutes for a long run is more than enough duration to be very competitive in races that last 60-75 minutes. What length race does that imply? Depends on how fast you are and how many miles you can cover in that time frame, and most importantly, if you even want to test the bounds of the upper end of the range of race distances in the first place.