We have health insurance, car insurance, home insurance...all just in case things don't go as planned. The more you have to lose, the more insurance you should have. Romantic? Nope. But how much of your day to day existence is all about romance? Stuff happens.
No matter how well you know someone, there are always a few doubts. People experience life grow and change...sometimes in different directions. It's not romantic to think about such things, but then, there's not much about a divorce lawyer that's romantic either.
Pre-nups are not the stuff of romance, that's for sure. But being able to talk about everything in a relationship...even what to do if the relationship ends, seems more healthy.