Automatic mergeAllFaces & fillet edge

I’ve been doing a bit of work over the last few days creating 2D dxf files for laser cutting from a 3D model.
Some of this involves altering the model in various ways so that the appropriate sheet parts will be able to fold correctly.

Anyway, I’ve noticed that many times I have to run MergeAllFaces on the 3D part in order allow fillet edge to work properly.

Over the time I was working on this, especially if I came back after a break, I’d sometimes forget to run this command, and then would spend a little time wondering what the hell was wrong with the part that it wouldn’t fillet, until i remembered to merge the edges.

So my question is, why doesn’t rhino just do this for me automatically?

I’m sure I could just put this into a macro, but why doesn’t rhino just not bother me and do it automatically?