Why do mafic igneous rocks lack quartz?
This will protect the walls around the sink from splashes They don't necessarily have to be made of quartz. I've seen them made of stainless steel. Personally, I wouldn't spend the extra money to have them installed if they were not already there.
I think it certainly looks nicer. And, if you get some water on the counter top and it pools next to the wall, the side and back splashes will prevent the water from damaging the wall. Otherwise, it's just cosmetic. I have granite counter tops in the kitchen and a granite vanity top in my master bathroom. We used travertine tile for the back and side splashes in a color that matches the granite, with an elaborate ogee trim around it. It really looks awesome, and so much better than if we had just left off the back and side splashes.
I agree that it certainly protects the sheetrock from water damage. If your sink is not terribly close to the wall, you would be all right without it. The side splash does finish off the top and covers any gaps between the wall and top....because quartz is tricky to install and you would be able to install one vanity top yourself, I would order the top a little undersized (if wall to wall) and then order the splashes to close the gap. I'm sorry, David, but I must correct your comment about color match. Quartz is entirely more consistent than granite. You should have very minimal color match issues with quartz if you decide to order the splashes later....Just make sure the color doesn't end up discontinued!!! Good Luck!!!
Once you realize you should have used them, you won't be able to match the counter top. Do it now, it's worth the extra money.
over time it will protect your wall from mildew and damage from years of water being splashed on it.