Before I take books to the charity shop, I check it wasn't a gift with someone writing on one of the first pages. I found a Rupert annual once with "To darling Sam with all my love, Grandma xxx "written inside it, and I found that sad.I guess some are donated by mistake, without checking.
I feel the same, but it sounds like a lot of folk wouldn't be bothered about that anyway. I'm not saying that they're wrong and I'm right, we're just different. You and I will think "But that was a beautiful gift, picked out specially for me and given with love by my cherished Grandmother"; others will think "That was very kind of her and I loved it so much when I was 8, but I'm 34 now, so it's time to move on and enjoy the present instead".
Some people possibly don't care about memories, but maybe, for many, they feel they don't need to keep the tangible item when the memory is safely locked in their head.
After all, the whole concept of nostalgia (and it's very name) stems from the belief that it was/is some form of illness, being caught up with the past and unable to move on with life.
I do find it remarkable, though, with things like concert and theatre tickets, where you could keep hundreds of them in a little shoebox and use them to remind yourself and relive all of those great memories for years to come. I wouldn't dream of getting rid of them, but lots of people just bin them as soon as the concert is finished, as to them, it's done its job and is now worthless ephemera.
Somebody else commented on the thread about things you resent having to pay for that they had to replace £50 in their child's Christmas card that they (the poster) had thrown out, without checking. Even I don't keep cards from neighbours and old work colleagues and the like, but I'd have thought that, if somebody is giving you £50, they're probably quite an important person in your life.
I suppose it's often two distinct mindsets, depending on your personal perspective: do these items help to preserve old memories or do they just clutter up and get in the way of being able to make new ones?
For some people, it's not even just physical clutter but 'mind clutter', where they delete all emails as soon as they've read them, even though they aren't taking up any physical space or more than a tiny insignificant fraction of your hard drive.