Here is what one of my writing folders looks like. When writing I often have multiple drafts of a chapter and I keep my old drafts. In the picture, you see 04.2 - Soul Stalkers. This is the second draft of the text and 4.1 is located in the Bits & Pieces folder.

Why do I keep the old versions?

Because sometimes I will make a major change and then decide the old version was better. Sometimes I want to remind myself WHY I changed something. Sometimes I will butcher a chapter so badly that I will need to go back to an older version and begin my edits all over again.

Never toss your old stuff. You WILL regret it.