The reason for using metaphors is because most users don't understand the more direct comparables.

Pretty much all non-technical users -- and a great many technical users -- have never heard of SafetyNet and don't know what it does.

Metaphors are imperfect; that's inherent to their very nature. That doesn't make them useless.

You don't even need to know what safety net is, the description after completely summarizes it and makes way more sense than talking about cash which I can't see any relation to the original topic.

I'm not sure how a non technical user is meant to get any kind of understanding of WEI from that metaphor. It can be explained quite simply "Websites can check if your browser has extensions or if your OS has been modified, and refuse access based on this information"

But that "explaination" doesn't really mean much to most people. It says words but does not say why they are bad.

It tells you exactly what is going on. It's up to people to decide for themselves if that's bad or not. I can't see any way to understand WEI going by the metaphore of buying newspapers. How does that explain anything?

It tells me what's going on, which is useless because I already knew whats going on. It does not tell anyone who actually needs to be told whats going on.