Why is it possible to assign no technique in an expression map?

I had a few staves that wouldn’t play most of their notation. When I looked at them in the Play tab, I saw this:

Note the lack of any playing techniques assigned to most of the notes. I tracked this down to mistakenly empty techniques in my expression maps:


The question I have is, why doesn’t Dorico assume the “Natural” technique in such a case? What’s a use case for a map with a null / unassigned technique?

I have encountered situations when auto-defaulting to Natural is actually not what you want. I can’t remember exactly, but it’s something like switching to another technique, then to a third, and then cancelling the last one and going back to the second.

How is this achieved with an expression with an unassigned technique, though? Why not just remove the expression altogether, since Dorico apparently interprets an unassigned technique the same as there being no expression for that technique at all?