ELI5: Why do computers just delete file pointers instead of wiping the actual data?

Computers only delete file pointers because removing a label is instantly fast and saves the drive from wearing out, whereas wiping the actual data takes a long time and uses unnecessary effort.

Imagine a giant library with millions of books, and at the entrance sits a massive card catalog that tells you exactly which shelf holds every single story.

When the librarian wants to get rid of a book, they do not run into the back room with an eraser to scrub away every single sentence on all five hundred pages. That would take hours, cause a lot of sweat, and eventually wear holes right through the paper.

Instead, the librarian simply walks over to the card catalog, pulls out the small index card for that book, and tears it up.

Here is what happens next in everyday life:

• Instant results: Tearing up the index card takes one second, so the computer feels super fast. If it had to erase every microscopic piece of the file, deleting a big movie would take just as long as downloading it.
• Open space: Even though the old book is still sitting physically on the shelf, the librarian now considers that spot completely empty.
• Natural reuse: When a brand-new book arrives, the librarian simply places it on that shelf, covering up or tossing out the old book only when the space is actually needed. This is called overwriting.
• Less wear and tear: Computer storage parts, like the flash memory inside your smartphone, have a limited lifespan and can only be rewritten a certain number of times. Scrubbing them clean every single time you hit delete would wear them out much faster.