There's a reason why they're not that common these days. They're expensive, they don't last long and they're known to have intonation problems.
Really, Segovia championed the creation of nylon strings for classical guitar nearly 100 years ago, and most people have never looked back. There are some purists who insist on gut strings for "historically informed performances" on period instruments. For the rest of us, gut strings are inferior to more modern alternatives.