LOL, puffling, I came on this thread specially to boast about having little geniuses We all know that the age when they walk and talk is soooooooo important for future success. Not.
On a more serious note, the "walking and talking" thing is a very common landmark for people to feel breastfeeding has gone on long enough. But it's wrong - there's good evidence that children benefit from bf long after the age when most are walking and talking - and professionals looking after children should not perpetuate this idea.
Put another way: a childcare professional advising a mother that breastfeeding has no value because the child can walk and talk might - not necessarily would of course - but might actually affect that child's health with their advice.
So, Mum saying "I've had enough, I want to stop" = great reason for stopping.
SN saying "You ought to stop, a 3 year old doesn't need bf" = a bad (because ignorant) reason for stopping.