It does have an aerodynamic effect at highway speeds, but it's mostly a cosmetic piece.
You can remove it without worry, or just cut slots into it for the tow hooks if you want to keep it on but want the tow hooks too.
I'd say removing it is a good idea for a vehicle that you're going to put tow hooks on, since it changes the looks slightly to give a visual "lift". Removing the plastic side skirts can be a good idea, too, both for the visual effect and to avoid the hassle of them breaking or coming apart off-road.
You can keep the plastic stuff for re-installation later if you convert back to stock or want to sell the vehicle without the mods, or just if you want to make a few extra bucks from someone who wants to buy the plastic pieces.