A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
I imagine that you may have gotten this file from someone else, or you created the locked shape yourself.
If it's from another source, the shape may have been locked in the Microsoft 365 version of PowerPoint. If you have Microsoft 365, open the Selection pane (Home>Select>Selection Pane), select the shape and click on the lock icon to unlock it.
If you have a retail version of PowerPoint (Office 2016, 2019, 2021), then you'll have to unlock it by editing the underlying XML of the file. Here's my how-to article: OOXML Hacking: Locking Graphics
This is not a problem with how PowerPoint is programmed, but rather how some people format PowerPoint presentations.