Welcome to the Quilting Board!
Honestly, I didn't really know people expected written thank you's for gifts. I got one once, when I was seven, after the birthday party for a girl in my class. I didn't understand why she sent it to me. I just wasn't raised to send out thank you cards. If someone gives me a gift and they are there, I thank them. If I open a gift from someone and they aren't there, I don't thank them because they aren't there. It doesn't mean I'm not thankful for the gift or that I'm ungrateful, they just aren't there. I honestly never knew it was an issue. These other people who don't thank for gifts could just not be aware, either.
As for those that receive quilts and have them stored away... my great aunt made a quilt that was brought to my grandpa's funeral. After the funeral was over, my dad got to keep it for his own. He keeps it folded on a wide hanger in a closet, covered in a plastic bag with an open bottom to protect it from any wear from other objects hitting it. It's not that he's unappreciative of it. It's that he -loves- the quilt and is afraid of using it, for fear of ruining it. So it's kept stored away.