I'd guess it's about the same number of people who used the exact same thing on a floppy disk.

It harkens back to cassette tapes (audio and video). Both had a tab on blanks that allowed recording. There was a pin in the recorder that, if allowed to extend, would prevent recording. So it would hit the tab of the blank and stop, and allow recording. Once you recorded the tape, if you wanted to protect it, you took a screwdriver and popped the tab out. (Again, the same feature existed on audio cassettes and VHS video tapes. But because audio cassettes could flip, there were two tabs, both on the top, one on either end, so you could protect one side but not the other... if you so chose.) The pin was very sensitive, all it took was your basic Scotch tape to cover the hole and unprotect the tape. This was by design. They wanted you to be able to record on the tape if you so desired, so yeah, you could record over a commercial tape if you really wanted to.

The tab on floppy disks and SD cards was a reusable cassette record tab. Nothing more, or less.

You're probably not wrong, though.