Why do many motorcyclists wear jackets in the middle of summer and en general, general during the summertime?

I've been noticing that for awhile now and at the same time was wondering why exactly do many of them wear jackets including leather jackets in the middle of a hot summer and en general, general during the hot summertime. Aren't they going to get hot later on? Don't they start to feel hot wearing their jackets while riding their motorcycles/motorbikes in the middle of summer and en general, general during the summertime?😕😐