Faith in a currency (points, dollars, euros) is directly correlated with your faith in the backer of the currency. Sometimes that faith is well founded, and other times, it's not.

I honestly do believe miles, points, etc, have inherent value. But that value is somewhere above value of fiat currencies in inflation rampant countries, and a bit below the value of stable, global reserve currencies.

All of these currencies have some degree of risk. You accept that risk when you do a conversion.

Taking your example in devaluation from 2014 to 2015 of your USDMs. Here's a good way to look at it from another angle.

And look on the bright side, it's better than currencies of countries that got plain wiped out. (Think confederate dollars.)