Just seems daft. Have gloves ever saved you? Thorns would just go straight through and they seem more faff than what benefit they can give you in warm weather. Why clad yourself/take yourself away from the breeze/feeling relaxed etc?
Road bike- I can see why you wear mitts- for the extra cushioning on your palm as the bike is bloody rigid but off road?
If you fall off- if you put your hand out your going break something, graze? How many times do you fall off with your hand out? I see them as just another layer/something to faff and remember.