Because the complexities of the whole region in general are ingrained over thousands of years of conflict of city states, then regions, then Empires, then religion, then inter religion conflict.
The area is divided yet linked through millennia of mutual history.
A boycott of purely Israel is...
Boycotts of any variety (as opposed to the concept of official sanctions) in the serious context of the Middle East is just more of the same old bullshit that leads to people not being able to sensibly talk about resolving their differences.
Unhelpful.