(SURE. I have so many headcanons for Castiel’s wings. I’ll try my best with this one particular canon I was going to use for the answer. I’m awful with writing!) 

So, an angel’s grace is what makes them…an angel, right? So, Castiel’s wings are a part of his grace. They are therefore (to me) an embodiment of strength, purity and goodness. So when a human touches these wings, they’re kind of connected with this grace. This feeling of comfort and serenity would fill them and it would be pretty great for someone like Dean or Sam. To be able to forget about how crap their lives are for just a bit. A bit like a high?

 Dean would be remembering when he and Sam were kids, the smell of his Mom’s hair when she scooped him up, the sound of her laughter. The sound of his Dad’s laughter, before the fire. Sam learning to walk. Sam smiling at him. You get the picture. 

But then it would also kind of suck when they stopped touching them. It would just be a temporary feeling, because angels aren’t omnipotent. They can only offer comfort. And once they stop touching, all the horrible memories would come back. 

But yeah, that was getting a bit complicated so I guess for simplicity, it just feels good for Cas to get his wings petted. And he would have pretty damn soft wings, so Dean would like it okay too. Maybe he’d get a vague nice feeling, but not this intense high I was gonna go with.

(In the show’s canon, the wings that belong to Cas’ incorporeal body would be difficult to manifest on Earth, and because they’re a part of his grace/true form, they would blind a human if he were to show them to one, let alone touch. I’m guessing. But for the sake of fun and this blog, we’re going to let Cas be able to let humans see and touch them okay :-))