There is truth that when you see a car with water spots all over it...its most likely a properly sealed or waxed car. Cars with no protection will not likely spot...its the other side of the coin so to speak. Having said that, its far better to have protection on your paint than not.
I think there is much to be said about the new coatings in this regard. I have Opti Coat and the water beads are so incredibly small, that its very hard to actually suffer from water spotting, which is a result from those large water beads drying out in the sun, then leaving a dirty water spot. I think the mistake guys make with these coatings (and I'm guilty myself from experience)...is that they have this irresistible urge to top the coating with a wax or another sealant, or even a detail spray product that has some kind of protection built in...which is a mistake in my opinion. When you top a coating with another product, the environment reacts with the topping, not the coating...and almost all toppings I've ever used, whether wax or sealant or fancy detail sprays...always result in huge water beads...which unfortunately usually lead to huge water spots if allowed to sun dry. My solution now with Opti Coat is just wash my car with a product that has no other quailty than to give me a clean surface...I don't want "extra" enhancers or waxes in my car wash because I want nothing to interfere with the Opti Coat. I also select detail sprays that do not put down extra protection, but are primarily for enhancing the gloss.
Ying/Yang...