1. In a proportional parliamentary system, most parties become highly focused. The good side is you have parties focuses on your agenda. The bad side is no focuses on the country as a whole. In a single member system (American style) many minorities are cut off from the political system. Netanyahu and Herzog aim their focus a bit higher, but so no interest in serving those who are unlikely to support them (note Bibi’s anti-Arab comments, and Arabs are the same percentage of Israelis as hareidim, and are much more likely to serve in the IDF). In the US, with only two possible choices, candidates focus on the whole electorate.
2. Under the current economic arrangements in Israel, most hareidi would face a very low glass ceiling. Why prepare for a career in an economy that considers religious accomodations to be something undesirable, especially if you a part of a minority that most Israelis would gladly be rid of. In the United States, law and custom are much more supportive of people like us working outside of the frum ghetto (but America has always been proud of its religious diversity). Remember the goal of zionism is a Torah-free society, and when they see a frummie it reminds them that they have failed to achieve that goal. Under these conditions, its rationale for the hareidi parties to focus on protecting communal autonomy. Why prepare for a job that discrimination won’t let you take?
3. In all fairness, hareidim who want a good parnassah tend to either go off the derekh and become religious zionists, or move to a country that believes in religious freedom. The fact that they choose to live in Eretz Yisrael, under a hostile regime, is indicative that they are primarily concerned with something other than making money (unlike their Brooklyn cousins).