[cctan]

I would like to upvote that comment many times. The price point for the deposit is important, why is this so hard to understand?

The reason it failed is because of this simple use case:

You want to return it just after you arrived, and it is still raining outside (this is why you rent an umbrella in the first place). If you wait for the sky to be clear to go out, you won't remember the umbrella. But if it is raining again when you go out, why would you want to return the umbrella???