In the real world probably very few people are interested in letting transactions if their wallet were 10% lower than yesterday. That was an example, of course.
With this said, basically all financial contracts (options, swaps, etc) are based on complex conditions of that kind that can easily be performed by Ethereum contracts.
The WhatsDApp example might be useless to you… seems like you don’t appreciate examples that are meant to clarify a technology that the majority of the people still do not grasp. If you asked a computer scientist how to decentralise an app of that caliber in untrustworthy networks you would be surprised and amazed. Only then would you start appreciating the technology. I personally understand your scepticism. If you are truly interested in understanding how certain problems are solved by Ethereum, I suggest you to read the whitepaper. It will take some time. But it is totally worth it. Warning! That is a technical paper.
Thanks for the comment