I use them for lots of things here, including cutting holes in doors prior to installing the latch/knob assemblies. Exterior doors are often clad in sheet metal, and the hole saws scuff up the paint around the hole edges by many mm.

And that's with 2-3cm of wood core inside the door to help center the bit. Not a precise implement.

For thin (most) sheet metal, step drills are best for small round holes, nibbling tools are great for small rectangular holes, and snips are hard to beat for anything larger.

Cheers