Although I presume your question is rhetorical, may I suggest a few reasons:

Skippy's New Years Eve Top Ten Reasons Israel Is Preventing The Press From Entering The War Zone! (to the refrains of The Who and "I Can't Explain" from Live At Leeds)

10. Ran out of luxury cots and pillows for their comfort during their stay;

9. Didn't like the cut of their jib;

8. They didn't say "pretty please";

7. Couldn't guarantee their protection from Gaza-based organ grinders and those annoying monkeys;

6. Misunderstood "enter the war zone" and thought they wanted to enter the war stoned;

5. Told them to come back after tea;

4. Knew they would write kind things and in all modesty had to decline, thanks all the same;

3. Just hate trying to get journalist blood out of their clean linens;

2. "Did we say you can't go in? Oh my no, be our guest, we'll be right behind you";

1. And the number one reason why Israel won't allow the foreign press into the war zone: They have something to hide! Wait a minute, the war zone is in Gaza. What was the question again?

Happy New Year, Peter!

I hope that someday we can put aside our fears and prejudices and just laugh at people.