I'm the same age as Zoe, as is my boyfriend and most people in our circle of friends. I have now seen two cases within our friend group where a couple has been together for years and years and the guy has not wanted to commit. The girl has given him an ultimatum, which has led to a breakup. Then the guy has immediately started a new relationship and within two years they have either been engaged or having a baby. This is a tale as old as time. It's not that he does not want to commit, it's that he does not want to commit to her.