The big difference for me is the context, influencers such as MrsM are based around being relatable, they live their lives like you and me. This is peer to peer marketing carried out in a sneaky covert way such that you don't realise you are being sold to. It creates a need for the same stuff that they are wearing/using/buying for their children that you probably can't shake or put your finger on (but swiping up makes it super easy to act on that need). Celebrities don't have that same context, you know they are famous and you aren't, your expectations around their wealth and means are different, so you don't feel that need in the same way and you may not be inclined to copy them to the same degree.
In reality the rules are no different though, celebs should be disclosing their ads and gifts in exactly the same way. ASA will judge them the same. TOWIE and Love Island 'celebs' are regularly ticked off for non disclosure. Holly Willoughby discloses her paid partnerships with M&S the same as the other fashion bloggers and should be disclosing her gifts and loaned dresses as well (whether she does or not I am unsure, I suspect not). I don't look at a picture of a celeb at a premiere though and think I must have the same dress, it isn't relatable in the same way as someone wearing a gifted coat from M&S or Next.
