The numbers speak for themselves - 1.7 Million tons of merchandise were imported into Gaza via the Israeli border in the last 2 years.
Israel allows in all the food and medicine that Gaza wants. Everything can go in, except for weapons and items that can be used to make weapons.
Same goes for the ability of people to cross the border for medical needs and for business. 10% of the people who crossed the border were internationals - journalists & aid workers.
Given Hamas' creation of terror tunnels used by it to carry out terrorist attacks in Israel against civilians, it is clear that there has to be control over what goes into the Gaza strip, so as to make sure that it is not used for Hamas' terrorist infrastructure.
With neighbors like Hamas, would you give up control over your border?