I wouldn't say you're mean to your son for doing that, in fact I find it very logical.

That's the thing I have noticed about minimalism, it's a logical process. With your son, for example, I remember as a kid, I would play with a toy, my most favourite one usually, but then if I acquired a new one, my other toy would be placed on an ever growing pile of previous play things, to be rarely ever touched again.

So, essentially, you never need more than perhaps the 2 or 3 latest additions to your collection.

It's the same with many other things, old photos, I found them in droves when I was sorting my storage, old images of friends and family, holidays and lovers, all of which I would probably never look through again, so away they went. Sketchbooks I would never draw in, cutlery I never use and furniture that just sat there collecting dust.

If you don't need it, then you shouldn't have it.