STL files are everywhere. When there’s something to 3D print, it’s probably going to be an STL. Which, as long as the model is good just as it is, is no trouble at all. But sooner or la… ...

Stereolithography, or STL, is the most common file type that makers use. It's also one of the oldest. According to Adobe, "STL was created by 3D Systems in 1987 as part of their stereolithography ...

I also tried 3D Studio files and STL files, ... Pepakura Designer comes with a few sample files of cubes andsuch, which are excellent for printing in color and testingyourself.

But if all slicers could directly input STEP files [2] instead of .STL, then the de-facto way to distribute 3D designs should change from .STL, which are harder to cleanly modify in a CAD program ...