Oh, definitely. Parties change, and people's priorities change, and that gradually leads to a strain. Even purely rational people have a hard time telling when that strain has become a breach.

And a new alliance isn't easy to construct. You can't just go to the opposite party and say, "I've swung to you, so start catering to my priorities". Usually, you'll spend some time voting for nobody, in hopes that somebody will notice you, but that's hard without some level of organization, and that's work. In the meantime, you're failing to vote for a party that you had at least some sympathy for, and possibly losing to a party that has no reason to be on your side.

So a lot of people make party-line decisions based on inertia. They could improve their situation, but it's not as simple as changing their vote, since the existing alliances have priorities that won't change for a few votes. That leaves a lot of people in limbo, where there is no really great rational choice.