Until September 2000 (Second Intifada), the civilians of Gaza entered Israel to work or for health care. There were over one million entrances every year. Although Israel continues at war with Hamas-Gaza, only in May 2017 there were 2,282 entrance requests, of which 47.2% were approved, 2.1% rejected and the rest were published in Haaretz but were not answered. One of the people that was assisted in health in Israel is a direct family member of Ismail Hanye, leader of Hamas.
The entrance permits for the sick that come from the Gaza Strip must receive authorization from the Palestinian Authority, but due to the internal war between the PA and Hamas, for long periods the PA has rejected granting permits to Gazans.
In 1979, Israel dismantled the industrial area in the Erez crossing. Thousands of Palestinians worked in the region. Dozens of attacks and Palestinian rocket-launching happened there. On June/8/2003, three Palestinians shot grenades and bullets, killing 4 Israeli soldiers. On Aug/31/2004, the Israelis captured a suicide terrorist. On June/29/2005 a suicide terrorist was captured with a medical permit while she attempted an attack against the Soroka Hospital of Beer Sheeva. On May/22/2998 a bomb-car exploded in Erez with hundreds of kilograms of explosives.
The honest question should be: why should Israel treat ill Palestinians from Gaza? In Gaza, the Hamas government acts to assassinate all Jews. If Israel assists Gazans, as it in fact does, it is only for humanitarian reasons.
We could also ask why the Palestinians from Gaza do not cross to and from Egypt, a country they do not wish to destroy. The most illogical blockade is the one imposed by Egypt.