Is there any studies supporting that after 65 it's unsafe? If not, why can't I fly until I can't get my medical anymore?
Why not? If you have a medical and perform well in the sim and line check then you should be allowed to continue in whatever capacity you have achieved.
I personally have no wish to continue beyond 60 years of age (at this moment in time), but who knows what life events may conspire to change the current view. (Could be divorce, could be the need to look after ageing parents)
Regards
Exeng