You are right, of course. When taking this poll, people compare life in the WB and Gaza compared to their lives in Israel. I also could not help but notice that the reasons cited are mostly financial. These East Jerusalem residents have been paying taxes to Israel for many years, in order to have health insurance and retirement benefits. It is highly probable that they would lose all that by moving to a Palestinian state. Most Palestinians in East Jerusalem are not well-off, this would present a great financial burden for them.
Iran: IAEA visit to U.S. Senate damages UN neutrality (DPA)
from the article: Would East Jerusalem Arabs rather be citizens of Israel or Palestine?