Radio waves became "useful" because people continued studying them. Neutrinos becoming "useful" would require us continue to study them, not waiting an arbitrary amount of time to study them.
The study of neutrinos is important to our fundamental understanding of how the universe functions. By themselves they might not have some earth shattering ramifications for our day to day life (or they might!), but there's a lot of unanswered questions about how things work at a really fundamental level and neutrinos are among the things we have questions about. Answering these questions would have significant impact on basically every other more "macro" field of study.
