I think (no actual proof) that actual complete physical inability to bf is rare. Reasons it doesn't happen though are many.
Regarding experience of 20mums I'm close to over last two years not one of us expected it to be hard as its natural. We all assumed it would just happen. All of us were told that baby knows what to do by NHS and NCT assistents. All of us were quite shocked when baby had no further idea than we did. All experienced pain in varying forms (nipples, let down etc). 10 switched to bottles inside first four weeks. 5 of those due to being twins, nicu/birthing issues. Further 5 due to actual bf issues. One for example only had milk on one side, another tongue tie etc.
Of the other 10, 8 had mixed fed. 2 exclusive bf. Of the 8 all switched to bottles totally inside 6mth point. Simplicity, ease, I remember being cited. The two who exclusive bf managed to keep it up for a year, starting weaning at 6mths also.
Now, two years on and some having a second child now, all state the biggest disappointment and regret was lack of support by others and belief in themselves.
Tips we learnt, tell everyone who has anything to do with your care about your bf intentions. Ensure its written large in your notes. Find out now from midwives if they have a bf consultant and how to contact her. In hospital ask as many people as possible to show you what to do. All of us who managed to bf found one person where suddenly it clicked. All of us also feel its important to expect the first month to be your time to practice. All skills require practice but for some reason we expect bf to work instantly. And finally, its one feed at a time. Shrink your world down. You aren't thinking of any further than just the next feed.
All of us found feeding fun, cosy, cheering and wonderful. We all just had different roads getting to that. Feeding is wonderful, however you do it.