My DM was like this when I was growing up, which she passed on to me. She'd buy me craft sets/stickers but I wasn't allowed to actually use them because then they'd be "gone". This was partly because those things were a lot more expensive in the 90s than they are now, but we weren't terribly hard up or anything. Plus, I'd still have the set but it would be in its complete form, which isn't a negative thing! For example: I had a candle making set that I wasn't allowed to do, and then when we finally did make one she wouldn't let me actually light it because then it would get used up!
I carried that thought of "don't use it or it'll be gone" with me until I had DD and she wanted to do those sorts of things and I thought, why not? Why am I saying no? I was never allowed to, but I'm not going to put that on her! Now anything she or DS gets can be opened and played with/made straight away if they like, because otherwise what's the point of having it? It'll just go to waste or gather dust, they should enjoy it while they've got it.
DM was very sentimental and liked to keep things nice. We were evicted from our house when I was a teenager, and I think DM got worse after that, because we'd had to leave so much behind and in such horrible circumstances. When I cleared her house after she died, there was SO MUCH stuff that she'd saved - stuff that belonged to her and my DGMs, who both suffered from the same compulsion to keep things for "best"! - and it was heartbreaking finding yet another unopened thing, or clothes with the tags still on. Most of it wasn't to my taste at all, or had gone bad, so it went to charity, was sold or thrown away. (She was definitely a hoarder, but a hoarder of lovely things! Still a hoarder, though.)
So now I try to use the nice things whenever I can. Sometimes I really will be saving something for a specific occassion, but otherwise I try hard to enjoy the lovely things people have bought me, or I've treated myself to.