Not sure where you are getting this. You could maybe argue that from a user experience point of view, it makes sense to be careful about what you add to material storage so as not to clutter that storage space. It's already big though, and that (potential?) issue is already mitigated with automatic organization and grouping. In my opinion this is either about user experience, or a lack of resources to make a low priority change like this happen. Easy to say you want this, but hard to pitch the idea to the decision makers when it's not that big a deal for most people. Even harder when an accumulation of this kind of stuff actually pushes players towards bank tab purchases... In other words, there is no reason they couldn't add baubles to material storage if they were willing to invest enough time, but there are probably a lot of things that the ArenaNet teams would like to see change. And those changes are inevitably going to be prioritized. This is probably just low on the list, if it's even on their radar.