There is no point of wearing a helmet if you are doing other irresponsible things which would dwarf the risks of not protecting your head.
No. The fact that you are exposing yourself to risks other than head injury does not lower the value of wearing a helmet. If there's a risk of head injury, wearing a helmet has a point.
No. In the way and conditions I ride, it doesn't make more sense as wearing it to get across the street. I hate to be told be less experienced where the boundary of reason lies.
When I walk in the street: no helmet.
In an elevator (and generally, in public places): no helmet
Whilst sleeping: no helmet (even when staying in earthquake prone areas).
Riding a motorcycle: helmet.
Skiing: no helmet, although it's the rule nowadays. The only times I did was when I was racing downhill.
Hang-gliding and paragliding: helmet (and chute!).
Airplane (as a pilot or as passenger): no helmet, no chute.
Glider: chute, but no helmet.
Kiting: no helmet, because I CHOSE safer places and conditions, and am unable to do risky moves.
Before a helmet, in order to minimise overall risk, I should reasonably take a floating vest, a whistle, and other props to make me visible if ever I go adrift, a greater risk IMHO than smashing my head on driftwood. I ride foils since 9 years and I've been told they don't relaunch ! So just in case it was true!
PS: In my area the only fatality I heard of is a rider who went off one afternoon and never returned.
In Mauritius, several riders got caught by currents and were never seen again.
Isn't this fixation on helmets as the ultimate risk prevention weird?