You would stop wearing a bike helmet if:

   - It made you top heavy and more likely to crash
   - It reduced your speed in half

The tacit implication (or elephant in the room) when someone argues for types and the presumed safety they bring is the severe cost they impose. Now they save some costs too, for sure. But the balance that I see is far, far in the direction that they save much less than they cost. (When applied universally as they almost always are when applied.)