While I am 70, and definitely not an "old fart" I seem to manage to keep track of what is around me OK. Many folks use a mirror to help, although, in the final analysis, it does require that one double checks into your "blind spot" by turning your head.

Perhaps by 75 I will have become an "old fart" and will respond differently - one never knows!!

And, I do not (and never have been very good at) riding with no hands, and yes, a whole lot of that depends upon the bike's geometry - especially the "trail."