Age does NOT have a thing to to with driver competence. It's an individual matter. It has to do with mental and physical state and eyesight. A good friend of mine actively roadraced a 1949 handshift WR H-D until he was 85. He passed away last year at the age of 89, sharp as a tack until the end.
There are a whole lot more incompetent young drivers out there than there are old timers.
2015 BMW R9T, 2010 Ducati 1098 Streetfighter S
2009 Kaw 650 Versys, 1967 Triumph 650 TT Special