Its simple, as well as the safety aspect polarized glasses are a tool which assist greatly in catching fish.
Earlier this year I purchased a pair of Amber Flying Fisherman Boca Grande glasses which I am very happy with for most fishing situations except very bright days when a darker lens such as grey is naturally more favourable. Wearing a quality pair of polarized glasses increases awareness and allows you to achieve a much better understanding of your surroundings.
You can purchase a pair for as little as €20 which is less than the price of many modern lures on the market these days but I would advise spending a little more if budget allows as the quality will increase greatly as will the protection from harmful UVA & UVB rays.
If you do not own a pair for fishing you really should !