Wet hair can be bad for your scalp if you allow your hair to stay wet too long.
The reason wet hair can be bad for your scalp is that the wet hair allows a breeding ground for bacteria which is fungus so fungus could grow in your hair on your scalp.
This is true especially if you go to bed with wet hair or cover your hair with a shower cap while it's wet and go to sleep.
After washing your hair and before going to bed you should always dry your hair off using a hair dryer.
Leaving your hair wet too long can cause fungus growth which is not good for your hair.
I always immediately take a hair dryer and set it on the hot setting and dry my hair while brushing it.
I don't like leaving my hair wet too long as I don't want to get fungus growth in the hair which has actually happened to me before.