If there are no leaks and all the fluids are topped up, there's nothing to erode or dry out. I know where your dad is coming from: my dad owned an 80's Mazda 626 that'd crap the bed every time we went on a vacation. He insisted on keeping our latter cars with friends on future trips and he'd call them to get them to warm it up and so on, lol.

Two weeks is too short for anything to occur (even tire dry rot) and yes, more harmful than good as others have said. I had the habit of idling my car after it had not run for a week and on the next start, it'd start rough... I'm guessing carbon build up. Bad habit and not worth it in the long run. Unless it's an old Italian car, it doesn't need the "Italian tune-up".