SFO-TLV is 7422 mi; LAX-TLV is 7574 mi... this is nearly the same as ORD-HKG, the longest nonstop on UA, so they'd need to use a plane with extremely long range (like the 777). That would be a significant investment, when instead they could just profit-share with LH over the Atlantic and let LH handle the TLV flight.

I would love an SFO-TLV direct, as I know many would... there are a lot of Israelis here, not to mention just Jews in general. However, based purely on population, I think it's much more likely we'd see an IAD-TLV way before an SFO-TLV... and that would also make airframe management easier, since many more planes could make IAD-TLV than SFO-TLV.

Finally... see this very relevant thread which includes similar discussion.