Because Hamas Charter prefers War to Peace:
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Israel will rise and will remain erect until Islam eliminates it....
The Islamic World is burning. It is incumbent upon each one of us to pour some water, little as it may be, with a view of extinguishing as much of the fire as he can, without awaiting action by the others....
For our struggle against the Jews is extremely wide-ranging and grave, so much so that it will need all the loyal efforts we can wield, to be followed by further steps and reinforced by successive battalions from the multifarious Arab and Islamic world, until the enemies are defeated and Allah’s victory prevails....
The time will not come until Muslims will fight the Jews (and kill them); until the Jews hide behind rocks and trees, which will cry: O Muslim! there is a Jew hiding behind me, come on and kill him!...
[Peace] initiatives, the so-called peaceful solutions, and the international conferences to resolve the Palestinian problem, are all contrary to the beliefs of the Islamic Resistance Movement...
There is no solution to the Palestinian problem except by Jihad. The initiatives, proposals and International Conferences are but a waste of time, an exercise in futility. The Palestinian people are too noble to have their future, their right and their destiny submitted to a vain game.
Hamas Charter (1988)