Agree with what everyone else has said.
Having unrealistic expectations about feeding frequency, pain etc. in the early days.
Not getting proper skin to skin after birth - they insisted on stitching me up straight away, that I couldn't hold him, could try feeding later, had an unsupervised trainee who had to re-do the stitches so took ages.
Unhelpful advice from HCPs - was encouraged to give formula in hospital to perfectly healthy baby to help him sleep so I could rest. Told to feed every 4 hours. Bottle feeding (either formula or expressed milk) was constantly pushed by midwives as the easier option - don't think it is actually easier than putting the baby on the boob.
A vague impression that formula was full of vitamins and minerals and perhaps my diet / stress levels / lack of sleep would mean my milk wasn't good enough - I guess I picked up this ridiculous idea partly from advertising of follow on milks.
Thankfully I had relations and a friend who had breastfed and talked me through the pain, told me it would get easier etc. And Mumsnet of course!
Also a supportive partner who although disappointed not to be getting more time with the baby realised that doing everything else in the short term was best for me and the baby.
So I guess if you have crap support from all around you and cultural pressure that formula is normal, its just too much after having given birth. I think also some women get pissed off with the pushing of breastfeeding while they are pregnant and automatically decide not to (have read that on here - not me I'm desperate to be a good girl!). And lack of decent maternity leave / convenient childcare means some people have to worry about getting them to take a bottle when they aren't around.