I agree, if your just reading directly from files (carefully) into structures then you don't need classes. You can always add methods to structs/classes for convenience. Adding methods to structures does seem strange, but works just the same.

However, if I'm designing data structures for an application, I will rarely, if ever, use a struct. I like to control access to my class members, knowing that there is only one possible place in the application that can modify key variables.