Why is Mom the Kid-Magnet?

So, last Sunday, I had a lot of studying to do. My husband was home for the morning and promised to watch our preschooler for me so I could get it done. I started out in the bedroom, reading my operating systems book on the bed. John (my husband) was making breakfast for Joe (my son). Joe starts out in the living room but then gravitates back to the bedroom. He was good - I'll give him that. He asked me to read him a Thomas book and when I explained to him I couldn't, he sat right next to me on the bed and read it himself for a very long time (relative 2.5 year old time).

Then, after breakfast I went out in the living room with earplugs and sat on the couch to study. John and Joe were carving a pumpkin. Somehow, John continued carving at the table and Joe ended up sitting on my feet with me paying him no attention and John trying every trick in the book to get his attention.

Why?

John says Joe never velcroes himself to him when I am not home. So it's just a mommy thing. John is an extrememly involved and loving father, and he and Joe are very close, so it surprises me that it is just me.