When I was pregnant with all 3 of mine, I would have driven some of you mad, as whenever my hands were not doing something they would naturally drift to my bump, it is just a natural instinct and much stronger with the first. It is an innate survival tendency to protect yourself, especially when feeling vulnerable. Khloe Kardashian was also criticised for the same reason. There are many reflexes and primitive instincts that remain with us, as humans, today. For many women, they will be unaware that they are instinctively "guarding" their baby. Is it really any surprise that someone so in the public eye during her first pregnancy may feel overwhelmed and want to protect herself and her baby.
Plus, as the baby develops they will react to being touched.
The personal interaction between the mother and baby should be respected, it doesn't matter if you think it is attention seeking, because she always has eyes and cameras on her watching her every move and documenting it in the tabloids, she doesn't need to seek attention, she gets it whether she wants it or not!
Also, Katherine did it just as much but she hid it slightly better by holding it with the hand that wasn't on display, but there are loads of pictures of every pregnant person in the public eye touching their bump from the moment of announcement.
She looked beautiful, and she appears to be loving being pregnant.