I think it's a lack of confidence or guts if you'd rather. There's a short window to fill in another class in your schedule so if a person thinks they'll drop later, may as well drop now.
You're a freshman, I take it? If you start giving up on shit as "too hard" now, everything's going to be too hard in the future. Learning only gets harder when you get older. If you need to enroll in a more remedial class first, fine, but don't waste your and your parents' money by avoiding classes that are "too hard" for four years of college. You are what you repeatedly do.