I agree. Taking care of your paintjob is really hard with all the knobs out there who drive crappy cars (or just don't give a crap about there car) opening doors into it.
I think your right about this one regarding the plastics/interior of the new cars these days..... but no matter how good the technology gets, your paint and leather parts will always be prone to damage from careless idiots. Even if a break-through is made on scratch-proof technology it will be some time before it is standard on all new production cars. I reckon if you love your car and you value the way your paintjob, leather and interior looks, its a worthwhile investment.