Sorry am too tired to attempt a link (up all night BFing baby who is going through a growth spurt LOL!)
There was a study published last year, part of the Million Women research project. It discovered - by studying a million women (quite a sizable scientific sample I'm sure you'll agree) that in cultures where women do extended BFing there is NO breast cancer.
The findings showed that where women strated having children in their 20s, breastfed for two years and had at least five children (i.e. BF for 10 years) - this acts to completely prevent breast cancer and it is unheard of in communities where women lead such a lifestyle.
Following on from that, the benefits clearly reduce if you have children later, have less than five, BF for a shorter time, but the benefits are still there, albeit on a reduced scale.
From the baby's point of view, Human breast milk is the perfect food - designed for baby and contains all the nutrients it needs. The fact that BF babies often don't poo for days or even weeks shows that the food is perfectly designed i.e. there is no waste.
I appreciate that many women cannot or don't want to BF for a variety of reasons, and that is their right. But their right to choose does not diminish the fact that human breast milk is the best possible food for babies. Its a fact, pure and very, very simple!
The OP was asking why people give up Bfing and the evidence from this thread indicated that it is often due to lack of support and advice available, rather than because they wanted to give up at that stage.