Do you believe in it? I came across a book written about this topic in the Adoptive Family magazine that came today.
I think that adoptive families (perhaps more so mothers) are under a lot of pressure to fall in love with motherhood and immediately bond with their child. Most often times in adoption you have waited years, maybe have had family and friends help fund your journey and perhaps it feels like all eyes are on you. And, after years of TTC, IF treatments, and waiting for the child to come into your life, perhaps the adoptive parents 'build up' parenthood into something it isn't.
Even biological moms often talk about how it has taken months to feel fully bonded (which is different from loving) to their child. Some have even talked openly about how it has taken them months to not 'hate' being a mom.