Is it true that period cramps get better after you'be had a baby? Whats the reasoning behind it though?

I experienced 1 period cycle after my first delivery, when my baby no.1 was about 24 months old. The menstrual cramps I had after birth was very painful and I do not think it is better off than before I got pregnant. Thus, it is not true for me. I asked some of my friends about their menstrual pain post delivery, some of them commented that the pain is still the same as pre-pregnancy.