Probably nothing - It seems mostly that people who cut gears in metal would not use paper templates.
In wood, I've cut gears with my CNC Router, that works great for wood precision. In metal, I get a gear cutter set and cut them out of blanks with a lathe/mill. Metal gears tend to be smaller and require much more precision. There's no reason why the shape of these gears wouldn't work, though.
I think usually metal gears are not cut by laser cutter or CNC router, but instead slotted using a milling cutter one tooth at a time and then the blank is rotated to the next position to cut the next tooth.
But of course if your metal gears are large enough to cut from the flat side then this template will work fine.
There are many ways to make gears, hobbing is one of the commonly used processes for cutting them from a blank. There is a cutter that looks something like a milling cutter, but it is turned in sync with the gear blank: https://en.wikipedia.org/wiki/Hobbing
