I had that mindset for years. But since I started using covers I definitely prefer them. Yes, there's an increased risk of scratching/swirls, especially if the car has modern clear coat paint (as this T/A does not). But paint is easily corrected, rust isn't. I'd leave a car uncovered in the rain and not touch it for a few days/week and then I'd open the door to find the jambs, door bottoms, etc still soaking wet. Same goes for any water that collects up in the cowl, rocker panels (a lot of wiper cowls drain out through the rocker panels), etc. Simply sitting in the open takes ages for it to dry. A cover prevents that, rain doesn't soak through into those low air-flow areas.
It's also a UV thing...The sun is likely even a bigger harm to cars outside than any rain/snow. It deteriorates everything; rubbers, paint, interiors, etc. Especially when we're talking materials that are already 30+ years old. A cover that keeps the sun off is a huge advantage.
So yeah, if you cover a dirty car and it's windy out; you're going to get some swirls. I always avoid covering a dirty car, but if/when swirls and minor scratches show up it's a lot easier to handle than the type of damager sitting outside uncovered promotes.
