I have absolutely no intention of stopping buying my nephews Christmas presents, why would I?
Well, no-one is saying you have to, but reasons many of us have are the sheer numbers.
10 nieces and nephews, becomes 20 once they have partners, then 40 once they have dc. My own dc alone used to be 3 people, but with partners that becomes 6 and - maybe one day, Grandchildren too. When does a partner make it on to the 'family' list ? How can you get a good present for someone you might not know that well ? Then, they move away for study, for work, for love, for adventure, so you have to factor in postage - not only the cost, but the logistics of it all. Then you might not see that niece that lives 300 miles away all that often, and that makes it even harder to get something they really like.
For me, it wasn't about money, but about stress and time. I will see my adult nieces and nephews sometimes, and will treat them to a meal, as we are close and I love them, but they don't need their Aunty to try to buy them a top which they probably wouldn't choose themselves or a book that they have already read or some perfume they don't really like to know that I love them. I hate waste, and to me, receiving presents I don't really like, is really wasteful. Even with lists, all of us trying to get things for dozens of other people, wrapping and the logistics of getting things to them, is all a bit silly. I have things I'd rather do with all that time saved.