Yes, they are a nuisance, but they were here long before you or your car so have more right to be here than us.
Frequent pooping is the result of their relatively short digestive system which aids them to stay in the air without being laden with a crop full of food. They have evolved that way because seafood is relatively easy to digest while releasing maximum nutrients. Now that they eat all sorts of stuff laying around they don't get the same goodness from their food so need to eat more frequently - so more poop on your car.
The reason they go so far inland now may be that humans leave so much rubbish around that the gulls have an absolute feast which makes them breed more. Competition at the coast is getting fierce and as there are more than the environment can support, they go inland to look for suitable breeding places and town's dumps and supermarket carparks for their food.
See if you can park your car away from light/power poles or anywhere from under were they like to alight on.
Bird droppings should be removed from the paint asap as the urea in it burns into the paint and will leave permanent marks.
If it is an unavoidable problem such as where you have to part at work, get one of those cheap synthetic tarpaulins and some of those 'bungee' tie-downs. Squeeze one of the hooks through each eyelet of the cover so you don't need to put them on each time and carry the cover in your boot. It should take you a whole 30 seconds to chuck the cover on and hook the bungees under the wheelbay or wherever you can anchor them. This will also preserve the interior and paint in the sun. It also slows down car-theft. If you haven't got a garage at home, it also keeps the frost off the car for that early morning start in the winter.
Now, aren't you sorry you asked? lol
*yawn* going to bed now.......