Well, there is a good reason for that. Their efforts, especially squirting water around after a vigorous chipping and scraping, sprays diluted blood all over the place. If you have Hep, HIV, etc. that blood is contagious, especially if it gets into their eyes. And, it will since the spray is partially an aerosol — which can,BTW, penetrate any mask.
Oh, yeah, believe me, I wasn’t questioning it. And yes, they also wear eye protection.