Here's a thesis which I may expound on eventually.
Between 1967 and the early 1970s, Israel sincerely intended on making Jerusalem a united city in the full meaning of the term. Sometime in the early 1970s, as the cost of pulling backward East Jerusalem up to West Jerusalem's level dawned on Israeli officialdom, while the international community hardened its determination not to enable Israel to maintain its control of the entire city, the budgets for the effort dwindled, and the socio-economic gaps never narrowed. Then, sometime after 2000, when it became clear that peace wouldn't happen, and the division was no more than a hypothetical but non-applicable idea, the officials began to move back towards pulling the East up to par. This, however, is totally unacceptable internationally, creating a situation which cannot be resolved in either direction. Systematic Israeli investments are forbidden, but damning Israel for their absence is fine. This, however, doesn't help the local Palestinians in the city.
There is ample documentation to demonstrate this thesis, though no one has ever tried, so far as I am aware.