K.P.
He's with you all the time... literally... so you are "old news". He likes to have physical contact while he's playing and simply stated- they are more interesting b/c they are "new".
I am not an "attachment" parent- we have never co-slept, I believe in CIO and learning to self-soothe, but cuddle and kiss my "almost 3 yr old" every chance I get. Having said that, the minute my BIL, sisters, parents, nieces walk into the house, DH and I don't exist anymore! He wants to play with them, read with them, sit with them... you get the idea. It's totally normal and it's a GOOD thing- this means that your son can detach from you without stress b/c he knows you are there if he needs you!