I would have been stoked to see the evidence of her sentimentality if that was my mother (my dad kept my stuff and I liked that very much). I guess we are all different people will different emotional reactions. Also I know nothing about you or your life so maybe your reaction is totally warranted.
What you fail to understand is that the vast majority of non-hoarders are still happy to get those "brief moments" of joy, memory, nostalgia -- connections to the past that could otherwise be totally gone. The cost is so low, the benefits -- perhaps not life-changing, but of a particular and hard-to-replicate quality that I think makes them worth it nevertheless.
For most people a reasonable amount of childhood memories doesn't cost that much to store (i.e. its taking up space you are paying for anyway) so why deny your grown up children the potential for enjoying them just because they might not care.
I also don't think your implication that only a small subset of people ("hoarders") will enjoy such collections is correct. Most people can become sentimental even if that's not their day to day modus operandi.
I would enjoy a digital hoard of stuff like that, but not a physical hoard. I have since digitized all of the stuff my parents hoarded and got rid of a lot of the physical items.
It doesn't really cost me anything on an ongoing basis to have this huge digital dump of files sitting around. It was a one time effort to scan everything. If my parents had done that and just left a huge archive of digital files, that would be fine.
If people feel neutrally about digital hoards, that makes sense.
It is amazing how things can be interpreted that differently. How heartless you have to be to not even spare a kind thought about the moments she lovingly put away the things for her loved child. If the person is a hoarder, they will do that for each and everything, not just for things that remind one of the memories of the loved ones.
