Problem here is, you wont get any replies that are very usable Abel
Some will say you should use sunglasses ALWAYS, and better not go out in the sun at all if possible, as it is hurtful.
Which is correct to some extent.
Others will say you should enjoy life to the fullest without the obvious downsides of wearing sunglasses in the surf and in heavy impacts from hydrofoiling or freestyle, and then protect your eyes when off the water.
So you could also protect your eyes most of the time, and be free when out on the water - that is one choice (like 99.9 % does it seems)
It is tricky though, cause there will always be individual stories about some who did get problems, when not wearing sunglasses.
And most will never know, as they dont wear sunglasses off the water either, unless in areas with high sun where it is pretty normal, off the water that is
Almost like discussing the reasons for cancer - tricky to say what causes or contributes and what you should and should not do...
PF