Hi,
I don't know why people do it or if there's any significance behind it, but I know a lot of people do kiss their beloved ones before the lid is closed. I've always done it as a last goodbye until we meet again, because it'll be the last time on this earth that I'll ever have contact with them. Although, I have heard it said that it's a way to help keep nightmares away, or give you peace. It doesn't have to be a kiss, just a touch of some sort.
Pam