It doesn't, at least for me. Perhaps you could explain your workflow a little more completely.
Thanks for the replies.
I now see that when I'm in Develop mode and take any action (hit Auto) it creates a "proof copy". How do I turn that off?
This is a deliberate safety feature whenever you have Soft Proofing turned on. The appearance of the image changes on the fly, and any adjustments you made in response to that may be inappropriate for the image when not seen in Soft Proof (and / or, when seen in Soft Proof set for a different output). So the current adjustments are protected, and a new separate copy is offered instead.
Press S to toggle this whole mode on and off. The normal working mode is off. The document background / surround changes to paper-white when Soft Proofing is on.
Virtual Copies made this way are automatically associated with the particular soft-proofing setup in force when they were created, and can be recognised by this being used as the Copy name.
So I must have pressed S and clicked the create virtual copy bar? And have turned on Proof in the Settings menu? I can't duplicate what was happening (a proof copy being created automatically on every frame that I made an adjustment with no clicking of any Create Proof Copy bar). Am I missing something? I don't use the "proof" feature so am oblivious to the ins and outs of all that. But it seems like an malfunction on LR's part to do what I was experiencing.
So I must have pressed S and clicked the create virtual copy bar?
The most likely explanation for being in Soft Proof, is pressing S by accident.
The first time you make any Develop settings change on a given image while in Soft Proof, you get asked whether LR should make a proof copy. If you say Yes, then that is what you are now editing. It's a whole separate image version appearing independently in the Filmstrip, in Library, etc - starting out with all the same keywords etc, although that can then be changed.
a proof copy being created automatically on every frame that I made an adjustment with no clicking of any Create Proof Copy bar
I think it's possible to check "always do this", then Yes and then not get asked any more: LR will just go ahead automatically.
To clear this behaviour, go to LR Preferences and click the Reset All Warning Dialogs button. Now it will once more ASK you each time you start to edit while in Soft Proof (with an image which is not already a Proofing Copy).
But the more radical and straightforward answer is not to BE in Soft Proof mode, except when you actively want that.