Take a look at the number of comments on this week's Carnival of the Cats and this week's Carnival of Family Life. I stopped by to say thanks in both places for linking to me and I noticed that the Family life one has about ten times as many comments, almost all thank you's, as the COTC. The lack of these has always struck me as a shame when I've hosted COTC. It's interesting to see that it's not like that everywhere.
I would argue that it's a matter of the moms who post things for family life being a different sort than the cat bloggers who post for COTC. It's more of a social group at the Carnival of Family Life and it would be bad form to not stop by and say thanks to the host.