When are sweatpants appropriate?

The Boy loves wearing his "fat pants" around the house and they do rather live up to their name. Not that I'm Little Miss Prim and Proper in the clothing department by any stretch of the imagination but I've allowed leggings to replace joggers as my comfort bottoms of choice.

However, this beautiful outfit on ♥Charlie breaks the mould on the lazy day outfit.

I can't help but wonder what she wore on her feet as I think that would be the deal breaker on this outfit if worn out of the house but there's no denying the cuteness of this outfit. I personally loathe to be in shirts and blouses as I find them too restrictive but I'm sure a nice basic tee would work almost as well with the cute cardigan.

What do you think, has this made sweat pants acceptable?