But it's still super cute!
You have a very good point
I've wondered about that myself...the only thing I could come up with is when you're holding them up on a table or something their feet don't slide out from underneath them. let's not worry about the fact they can't hold their heads up...just make sure their feet don't slide...;-)
They put those little anti-skid thingies there to make the socks look cuter - and more buyable...