[Aliantha]

If you transfer the contents with preserves, you risk contamination and the contents have to be refrigerated and usually consumed in a short period of time. With proper preserving, the idea is to add the preserve to the jar then put the lid on while it's still close to boiling if not still boiling.

I understand your point, and while it's a good one for non-preserved things like lollies etc, it wouldn't really work for jams and things like that.