When all is said and done, the purpose of a jig is to keep a consistent angle (or distance or position in other scenarios). A straight razor already comes with a jig that does not require configuration, and which is always the exact same angle, regardless of where and when you use it. That built-in jig also happens to be set at a very convenient angle (or range of angles when compared between individual razors) that has been used for centuries.
It's free.
It's foolproof.
It's consistent.

So, what's the point of adding additional contraptions?