My father once gave me a gift which his father gave it to him. Which is basically a wrist watch that automatically winds a spring inside while a person is walking. That watch is practically useless by today's standards. But that is totally besides the point. He gave it to me because that has some 'emotional value' and the fact that it was expensive at that time, and his father went through a lot of work to buy him that has some sentimental value attached to it. That is the whole reason behind its existence, He gave it to me because it means something to him. Many of my friends have asked me if I want to sell it, but I've turned them down. It looks awesome and is a jewel.
My mom also wears a diamond, and she has told me once she passes away that is supposed to given to me and never to be sold to anybody else. No, De Beers didn't whisper in her ears not to sell it. Its just my dad gave it to her and that diamond reminds her of her days when she was young, and the moment when it was given. That thing reminds her of those days. She just doesn't want some other women to wear it.
You can argue these things in the investment per se. But you don't give the diamond to your girl and that moment is gone forever. You can earn that money back again, but you can't earn that moment back. She won't have that diamond with her which she can remember you gave it to her.
As nerds we can argue about rationality, but what is that worth to human sentiments?
Besides you can expand this argument to everything around. And the only way to live will be to live frugal.