I have an aversion to powdered milk and figured that since breastmilk was free I'd use it.
I didn't know how to make up a bottle and didn't know anyone to ask who wouldn't think I was really stupid.
I wanted to breastfeed for health reasons for both DS and myself.
I am far too lazy and disorganised to do anything other than breastfeed - I'd have forgotten to make up the bottles and DH would've mucked it up somehow too
It made going out easier - especially since DS was quite sicky and needed many changes of clothes - bottles would've taken up much-needed clothes/muslins/wipes space on my pram (don't have a car)!
It meant DH made my dinner while I fed DS.
I enjoy it and DS enjoys it (he crawls up to me making smacking sounds with his mouth when he wants to nurse now).
DH had all kinds of orthodontic work when he was little and breastfeeding is meant to make this less likely because of the different sucking action making mouth development different.
I liked seeing DS grow and knowing it was all my own work, just like when I was pregnant with him.
These are all reasons that won't apply to everyone. They're my personal reasons for breastfeeding.