The Hamas al-Qassam Brigades website has a long
article bragging about how successful they believe they have been in kidnapping Israeli soldiers over the decades.
The headline is most instructive as to their goals in such operations:
Al-Qassam Brigades ... a long history of abducting soldiers and humiliating the Jews
Of course, this is another attribute of the psychological projection that most Arabs have; they are deeply humiliated every day by Israel's existence and they think that this is Israel's raison d'etre; and their goal is likewise to pay back that humiliation.