What are you hoping to achieve buy not using it..?? So its gets dirty who cares. It's just a car at the end of the day so you should enjoy it for what it is. Are your hoping that the value is going to start going up. I believe the only way that will happen is if when you buy the car brand new, you seal the car in a vacuum packed bag and store it for at least 25 years. People do actually do that.!!!
Most people have done so many mods to there cars that it would probably put potential buys off.
But I know we all buy these cars for different reasons and drive them in different styles so if a clean car gives you more pleasure than driving it then it's all good