What's the point of Item Exchange event?

I noticed the event "Item Exchange" which is available via the Festive Balloon:

In this "event" we can replace items (stones in that case) with items that when used, provide those same exact items again.

I gave it a try, and there's no bonus or additional items while doing that.

What is the point of this event? Why would anyone want chests instead of the stones?

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