“Siri” has existed for a long time, yes. Apple Intelligence, not so much. It really is just an arbitrary AI model, since I’ve had Siri for a decade and not needed whatever this extra 13GB model is.
You've had a previous version of Siri for a decade that didn't do what the current version of Siri does. Whether you use it or not is not germane to whether the model is justified – it's what Siri needs to do what Apple wants it to do.
Siri didn’t always have a multiple gigabyte installation surface.
Sure, it doesn’t bother me that I can’t uninstall Siri or Apple News or Stocks on my Mac because those programs take up a trivial amount of space. I can just disable or remove them from the dock and move on with my life.
That’s not the case now that “Siri” is a double digit gigabyte installation, especially if you assume that my computer has 256GB of storage, which was almost certainly Apple’s most popular MacBook Air configuration within the last 5 years.
That is a new change where Apple is using 5% of my storage space for something I don’t even want to use.