Simple. The Orthodox political parties have a narrow agenda. They only want a few things and are willing to form a government with secular parties in exchange for those things. For example, in the past they have formed a government with secular parties and the only thing they really cared about was FILL IN THE BLANK (money for yeshivas, control over marriage and divorce as well as conversion, etc). If they get that then they do not care that much about the other stuff. So, they have cared about issues such as the "who is a Jew," debate, marriage, divorce, and all that more anyone else while everyone else was debating economic policy, military spending, the peace process. You get the picture. THE problem occurred when secular parties allowed for the exception of yeshiva students from military service. It is rare for a political party to win an election outright and attempt its agenda without selling its soul.
Israeli forces demolish illegal houses, power infrastructure in Palestinian village Aqaba (Haaretz)
from the article: The real threat to Judaism's renewal