In my opinion, this is no different from saying there's no need to watch new films or TV shows that come out, or even older ones that you haven't seen before. Why do that when you can just watch Seinfeld, Breaking Bad, the Godfather, and 2001: A Space Odyssey? Why check out books you haven't read before when you have [insert childhood favorite]?
There's absolutely nothing wrong with repeatedly returning to old stuff you like. But I don't see how people can be satisfied doing nothing but that. Fantastic new art is being created all the time, and the amount of people creating art is also increasing all the time.
The point of endless digging is to try to find other stuff that you may end up liking as much as, or perhaps even more than, the older stuff. It's not simply to consume for its own sake: it's to discover things you otherwise might be missing out on and would be thankful you found. How can you even know if that'll happen or not if you aren't exposed to lots of new things?
Also, what does it even mean to "endlessly collect" music in the modern day? You just listen to stuff you haven't heard and turn it off if you don't like it and save it to a playlist/favorites list if you do like it. There's no cost to trying albums you haven't heard before, like there was in the past. If you do really want a physical copy for whatever reason, it's easy to listen online first and decide whether or not you should get the physical copy.
This seems akin to lamenting that people are "endlessly collecting" new shows, films, and documentaries by browsing Netflix.