I believe creators should have an option when publishing a collection to opt-out of the allowance of VRM export from the backpack. This is a great feature but some creators may not like the idea of freely allowing anyone and everyone to export their wearables as VRMs to do whatever they please with.
I understand this is possible with downloading the assets as GLBs, but GLBs aren't as widely compatible in avatar marketplaces as VRMs are.
With the emerging platforms that are VRM compatible and allowing free distribution of VRMs, it takes a lot of power and control away from the Creator. It could be a simple toggle to allow or not allow VRM export.