This is not an argument you want to follow to its logical conclusion. This kind of choice is the slippery slope that leads to athletes taking performance-enhancing drugs and other things that have a high risk factor but potential benefit in terms of on-ice performance.
The "damn good reason" that athletes choose not to wear optional protective gear, such as visors, is because of the perception (real or imagined) that they perform better without it. I think we can both agree that the athletes likely have very good advice in terms of understanding the risks involved and the potential benefits of wearing this gear. If they choose not to, I think we can also likely agree that they do so, almost without a doubt, that they feel they perform better on the ice without said gear. Athletes look for advantages they can exploit, including in terms of their gear.
However, if each athlete was required to wear the protective gear, no one would be at a disadvantage by wearing it. Everyone would receive the benefits of the gear, and everyone would be subject to the drawbacks.
That is why people make the argument that the gear should be mandatory. Every player that chooses to wear the gear today knowingly gives up some perceived degree of performance as compared to his peers. That perceived disadvantage would disappear if -every- player had to wear the gear. But I would wager my life savings that we will never see a majority of players wearing visors until they become mandatory. No one wants to give up the advantage, because relatively few people lose eyes/take permanent injuries. Thus the relative risk is low, even if the potential consequences are devastating.
