There have been some rockets from Sinai whose origin points in ISIL's way, and in addition they're very supportive of others attacking Israel as well. So don't think that they're buddy-buddy with Israel, as a lot of people have hatefully suggested.
One huge theory as to why they haven't attacked Israel is essentially because they don't want to bring them in. True, they have attacked other capable of invading them; however, with Israel it's a bit more of a guarantee that they won't intervene if you don't provoke them too much. Israel keeps to themselves when it comes to other wars in the Arab world that don't involve them, so by not directly attacking them they can avoid Israel throwing themselves in. Israel is also right there and would bring a very strong force with them, so the ability to put off attacking them in favor of others who will attack regardless is something ISIL does take advantage of.
There is also the fact that ISIL makes a stronger statement with some of their attacks. Attacking Israel won't deliver the same messages as attacking France would, since no one cares as much about Israel in comparison. Using Beirut and their tragedy, you can see that the world does place more emphasis on the French and the shock value is stronger there. The world is used to Israel being the target, but it sends fear down many people's spines to think that France was that vulnerable. Also, the fact remains that Israel doesn't take many more Syrian refugees anymore (they've taken ~80K in the past, though), whereas France does, and it's thought that their attacks weren't just against the West but to also make things harder for the people fleeing them as well. Attacking Israel won't get that for them.
Lastly, there is the fact that ISIL's intelligence gathering and infiltration capabilities in Israel wouldn't be as strong. One thing people are concerned about is the refugees of Syria are double agents, and obviously not as many are entering Israel. Aside from two Jews from their very reduced Jewish population, it seems like the rest of the people who have attempted are those who have little choice and desperate need of medical attention.