I've done some mining. I didn't buy cards for it, but my RX480 has basically paid for itself (bought it last year, mined this year through june 2017).
And i agree some people are salty because they see other people making some amount of money from it but they can't be bothered making the effort to do so themselves.
I have not now, or at any point in the past set up a crytocurrency mining rig nor earned a single bitcoin, etherium, or whatever is popular now. Stones shall be forthcoming.
Wait before you pick up that boulder - consider some of the profits (recent stock reports!), and innovation this "new" boom has driven to some of the companies we all love! Extra jobs and on it goes. It may not affect us in a direct/tangible way, but it has affected all of us.
Well, it did drastically increase the resale value of my R9 Fury X, decreasing the cost of upgrading to an RX Vega 64 substantially. So I guess it isn't all bad.