In the case of personal files: probably true. Who needs 20y old tax filings.

But there are exceptions. For example: sometimes games were released (binary only), decades later an author dies, relatives clean out the attic & flog some old computer junk on eBay, buyer goes through the stuff & discovers source code for a game that was believed to be lost long ago.

Or a never-released book manuscript is discovered in similar fashion.

It's not often, but it does happen.

Except the fact that there is still tons of old un-archived software out there in the wild because we used floppies for decades.

One of the greatest things about the retro computing community is when they buy or find old software they tend to try to image it and put it up on archive.org.

So much software has already been lost to time unfortunately.