Turn that argument on its head: If you have the reflexes but not the experience, it'll be okay provided you're not in a situation requiring much experience?
All the experience in the world isn't going to help your pax if your heart finally decides to give up the ghost, or you don't pick up that glider cloud soaring through your chin bubble, or that wire in the marginal weather, or a moments inattention means a crucial missed radio call. The chance of that happening in a post 60 y/o pilot is significantly higher (cue: demands for statistical proof
).
Hey, that would make an interesting comparison: which is statistically more likely to quit - the engine (re: single/twin conundrum) or the experienced pilot's heart
Joking aside, being a helicopter pilot can be considered a demanding occupation. The standard expected when carrying pax is high. A duty of care is owed to those people to ensure they are not exposed to a greater risk that they have to be. In an ideal world pilots would be an "on condition" commodity. But there comes a point where the human body is too unpredictable for that risk to be taken.
Experience is invaluable, but there are some times it just won't cut it alone. Some things just need cold, hard reflexes. Just like when you tell the student that knowing the flight manual and CPL syllabus inside out isn't going to save his ass all the time, some things you can only learn through experience. Not to run before you can walk is an important lesson to young pilots. Learning when to stop running and start walking again is probably an equally important lesson. The crucial difference is that an inexperienced pilot will continue to gain in experience, becoming less of a liability with time. There is no way but downhill when your reflexes start to go.
As a low hour, inexperienced pilot I have many people above me in the food chain who will constantly remind me of the fact. And this will be the case for many years to come. But when you reach the higher echelons, who reminds them of their limitations? Particularly the incipient deteriorations that sneak up with age. You think the 20year old line pilot is going to have a quiet word with his Chief Pilot telling him that he thinks his awareness is slipping, or he was a little slow responding to something? In reality, probably not. Which is where the higher authority pops in - the law, setting down a maximum age.