There are some things like booleans that do extrusion in them that use the relation of the line to the object being cut to determine an extrusion direction.

That's why a boolean with a line like these works:







But if you're just doing a regular extrusion of the line rather than using it as a cut there isn't a secondary object to help it pick which direction to go in.

I guess I could try something like look at what viewport you clicked in and if you clicked in the front view then make it go normal to that view...

Currently instead of using the "Set dir" you may want to instead just draw a little additional leg onto the line then that makes it define a single plane.

- Michael