Comment by Cthulhu_

And that's consumer apps, having only glimpsed in the world of back-end / cloud shenanigans, there's heaps of data being generated and stored in datacenters. Useful data? Dunno, how useful are all access logs ever?

But it's stored because it's possible, easy, and cheap. Unlike older games, where developers would hide unused blocks of empty data for some last-minute emergency cramming if they needed it.