Good question.
I've always been interested to hear what Rey had to say about putting his mask back on. I'm not overly familiar with Lucha culture, SGL might be able to answer this, but isn't it a major offence to put your mask back on after you've 'lost it'?
From a fan perspective, it was easier to accept Rey bringing back the mask because the majority of fans were more familiar with him being masked and it's WWE cannon.
Plus, Mysterio wasn't supposed to be horribly burnt. Although, that was becoming harder to suspend my disbelief for when Kane kept returning with more revealing clothing each time.