Reed1,
"As adults are you not in any way capable of buying all this stuff for yourselves at some point, instead of waiting for some other adult to buy it for you."
"As I said on the similar mens thread. Buying for adults is just ridiculous."
"Being an adult means that Christmas presents are over."
In all cases? I disagree there.
Yes, of course most adults are capable of buying for themselves.
Doesn't mean they're always in a financial position to do so, and therefore not appreciative if somebody generous can afford it instead.
Or maybe severe health problems prevent such.
My M.E.-suffering friend certainly won't be up to shopping/ organising/ joining in with social stuff this year.
But, hey, she's 43, so I needn't bother buying her a gift, need I?
No point whatsoever in a small "thinking of you and know you're here with us in spirit/M.E. was a total bitch to you in 2017, but you're still surviving and a brilliant friend" present..Nope, she's over 18.
Albeit one unable to physically partake in your idea of a meaningful Christmas and so can just remain isolated and unfestive.
Or a particularly stressful/traumatic year has meant the recipient's own needs have gone neglected in favour of other people. And a gift means a huge amount to them when someone has noticed enough to spoil them for a change.
Or they've gone above and beyond supporting the gift-giver, who wants to show genuine appreciation by finding them something special.
Or, much as giver and recipient might love to spend time enjoying each other's company in person, distance doesn't permit, and a well-chosen, thoughtful present helps bridge the gap in the meantime.
And tens of other reasons...
Not everyone is lucky enough to have in their lives, let alone spend the festive period itself with, close-knit and loving family/friends...or young children to focus on.
Pretty insensitive of you to imply (on TWO threads specifically about present-buying 
) that looking forward to a few given treats to brighten the day makes them "ridiculous" and "childish". And/or more concerned with materialism.
Do agree with you that it becomes pointless when gifts get given/received in begrudging/ungrateful spirit, devoid of any genuine feeling from either side, and cause major hassle all round, though.
(Am not talking about the usual light-hearted grumbling over buying that we're probably all guilty of at times, but the situations when real anger and resentment lead to all sorts. See many MN threads).
TL;DR
This, and the Men's equivalent thread, is proving very helpful to a lot of us. Why come onto an adult present ideas topic, only to insult...er...adults buying presents for other adults?