Basically anyone who washes their hands frequently (ie all medical personnel, food handlers, etc.) or does manual work with ungloved hands (including home gardening) can later in life have fingerprints so abraded as to be unidentifiable. Using a lot of hand lotion, as anyone with dry hands might, also tends to flatten the ridges. Any requirement for fingerprints as a biometric can render systems inaccessible for entire classes of people - it's a growing problem in banking for the elderly, for example.