Software is a tool. Software is infrastructure. Degradation is desirable in neither.
Data has metadata - creation time, access time, etc. - that can power workflows to identify and deal with old data if that is desirable, but in most cases they are not desirable. I haven't looked at the directory full of my wedding pictures in a decade, but I don't want my photo editing software to decide they're irrelevant and delete or hide them.
Having access to old documents and data is often important and beneficial. It's why people look at inscriptions in old books, why they keep photo albums, why finding a forgotten item when moving furniture can be delightful. It's why we're able to identify trends.
Most crucially, it is incredibly difficult to predict in advance which data will be useful in the future. Proactively discarding things when storage is incredibly cheap is a net negative.