That EC2 example is a bit extreme, but in general I agree with what you are saying. Unfortunately, the reality is that most people paying for software development are more willing to accept these risks than to pay for security.

That said, security is not all-or-nothing. And anyone who believes that modern web-connected software can be 100% secure is either misinformed or trying to sell you something that you probably don't need.

If instead of exposing your API keys you implement an API that proxies that responsibilities your app would have needed those keys for, how are your API keys not 100% secure? You even get the added benefit of separating the implementation of those responsibilities from your app (and with app update processes being what they are, that's a huge deal when you need to make an emergency change to how you're using those APIs)