It wasn't suddenly. It was gradually. Over an extended period of time it became obvious the support planets rule was confusing, irritating, poorly defined, unnecessarily restrictive and just generally not a good thing. No one moment decided this, which is why nobody has pointed one out. If someone signed up like 800 planets to support their tag I imagine something might change. Certainly without the existence of a systematic campaign to utilise support planets I can't see anything being done. As I pointed out all those planets combined add up to something like 5 or 6 def fleets sent to ascendancy. This is about as game changing as a big planet that meant to launch on ascendancy launching on some random co-ords by accident instead.
I'm going to provide a visual aid to what you're doing here
It's a molehill someone turned into a mountain!
I'm going to provide a visual aid to why you're doing it as well
I don't really think this one needs an explanation...