A lot of misconceptions posted in this thread.
1. For the general public, you can boil down the use of ceramic coating to this statement: It's a longer lasting wax (yeah, I know its not a wax, but your benefit is basically that)
2. Ceramic coating won't product from rock chips, so it's dumb to compare it to ppf. It can help against chemical attacks like bird poop or tree sap.
3. People who get ceramic coating confuse the coating with paint polishing, as the professionals upsell them.
That's why some people think ceramic coating is a $1500 process, when its actually a $60 product you can apply yourself.
Why do it? Because you can wash your car easier. It's like your car is always freshly waxed. Dirt falls off the car, and after I rinse it, the water sheets off. 2 years strong on my carpro ccquartz application, should last another 2 years or so before I would need to consider applying again.
As far as ppf goes, get the front bumper and hood covered. Maybe side view mirrors, headlights, a pillers, and lower side panels too if you want. No reason to cover the side and rear of the car. That's a waste of money. Rocks aren't going to be hitting your car from those directions. I have full front ppf on mine.
tldr: Like to keep your car clean? ceramic coat makes washing easier. Don't like rock chips? ppf on the front can reduce them to almost zero. Especially with the thicker films available today. If you don't wash your car often, or don't care about rock chips, then save your money.