:( :(
It's so not 'arbitrary' when babies take/don't take to the breast.
Early breastfeeding is hugely influenced by birth and perinatal events and treatment.
Some babies do get over a difficult start, some babies manage to overcome heavy-handed shoving and grabbing, some babies can withstand not being given that all-so-important skin to skin...but some babies don't, or if they do, it takes a while, during which the mother may lose confidence and belief in herself and have an all-round miserable time.
If we get birth and early postnatal support for breastfeeding right, we will find far more babies are able to breastfeed happily and effectively; the ones who still have serious difficulties or whose mothers have serious difficulties, will be able to access the time and the expertise for these issues to have the very best chance of resolving....and the support and care they need to rebuild their confidence if the problems persist.
But honestly - in most cases, not arbitrary :(