Paint always fits perfectly, like a person's skin. It doesn't need special care while washing - it simply goes away. No need to worry about using the wrong kind of detergent or the colours fading.
Paint can make someone as colourful as they want, or as red as they prefer.
Another benefit of paint is that there's no limit of patterns and designs. With clothes, you're restricted to what's available in a shop - or you can throw a lot of cash at a designer to make something. But who wants that?
Life is about expression and joy. About liberty and feeling good. For naturists, this doesn't involve clothes, so stick your designers where the sun doesn't reach. Regular clothes are okay for when the weather goes south (or north, when you're in the southern hemisphere).
I'd love to live in a world where bodypaint would count as clothing. The multitude of possibilities is something I'm looking forward to, even though it's probably not going to happen in my lifetime.
But who knows... Let's never say never.