I've spent a TON of time looking at IDF AR15s while doing research for my IDF clone. Outside of their flashlight mount and magazine holder, I have never seen a FAB Defense part on any IDF guns.
1. The IDF does not throw anything usable away. The standard issue stock for the IDF is our GLR-16. That does not mean that they go through all of their old carbines and junk the usable CAR or M4 stocks and install GLR-16s. They put them on new carbines, they replace some old stocks, but they phase them in instead of just replacing all of the old equipment. The emphasis is strongly on training over equipment, and they would rather keep the economy of using the working gear they already have and spend more money to train with it.
This is why you will see tons of beat-up old carbines and rifles with carry handles and no brass deflectors, cut down barrels to make carbines, old CAR stocks, rails added to standard polymer handguards, etc. This is why the PEC ejection port cover was built - so worn uppers that will not hold an ejection port cover closed anymore can still be used by adjusting the height of the PEC's detent. This was also the reason that the UGC noise and movement eliminator was developed. It is not really needed on many weapons, but those beat-up old M16s in Israel were getting pretty sloppy.
Even in the special ops units that tend to have the best gear, you will still see a mixture of older and newer stuff. Like i said, they are just more worried about their ability to use the weapon.
They generally don't buy their own gear and are not allowed to. Fortunately for them, they do not need to as Israel led the world in developing and issuing modern weapon accessories when the US issued nothing but a cleaning kit and nylon sling with the M16. In fact, if you talk to a some of older US SEALs from the 80s and early 90s and before, they all know our stuff and many used it as well as they worked closely with Israel at that time and a lot of this type of equipment was not yet available anywhere else.
2. Most of the images that can easily be found of the IDF soldiers tend to be a bit dated and there are not many current photos of soldiers in some of the special forces units. There are a lot more photos out there of soldiers in support-type units. Keep in mind that these guys are operating in an ongoing war that takes place in their own communities. These guy's families live where they operate and they are a target 24/7, so they tend to avoid publishing a lot of current photos.

