The first year I had chickens they wouldn't go in. I would chase them all around trying to heard them in and get soaked in the process!
I finally chalked it up to them being young and not having any older chickens telling them what to do. Once the boys figured out I wanted them in when it rained they hustled the girls in. . . well most of them anyway.
There are always one or two girls who think it's O.K. to get wet and beraggled. Now that I have mixed age groups the younger ones generally follow the lead of the older ones. Same with nesting box behavior. The new girls always watch the older girls nesting, act facinated by what they are up to, and when it's time they go into the nesting boxes also. Not so with my first year girls. They didn't seem to have a clue and were laying all over the place. I put fake eggs in PLUS had to show them a few time by putting them physically into the boxes. What a whoot!