I guess multi party systems and having a political spectrum go well hand in hand. A party in a multi party environment cannot entrench against "the other", at least not all of them. It must stay open for negotiations if they want to be part of a coalition forming a government. Since these compositions may change based on how the people vote, parties need principally be able to talk and govern with all other parties, to get anything of their own agenda done.

On paper this sounds like a recipe for "nothing gets done", since power is fractured so much. So I'm still wondering. It's a great question. Also a loaded question, which isn't that easy to quantify.