I find skymiles to be a joke, but then I did some research in to the situation.
If I open a Delta skymiles credit card I can receive 50,000 mile sign-on bonus with i think one or two free passes to the admiral club ($50 value). I have my first years fee waived, but its a $95 annual fee.
BUT than the card entitles you to these Delta "perks". Like I want to say you get sky priority check-in and bag checks (all these things they nickel and dime people on, like get your bags faster after landing with priority bags and shit). Most importantly you and like 7 of your passengers first checked bags fly free. So if you bring just 1 person with you on a vacation you will pay 24 x 4 just in bags for you and your friend to go on that trip.
Then you can use delta skymiles site to purchase shit. I work in the IT field and I am always buying shit and I buy from newegg through Delta skymiles because I get half a point for every dollar spent. And if I am buying shit for my employer this way (where they spend a couple grand a year in our department on websites like newegg) I can pull a few thousand miles a year that way.
Plus delta gave me and the person I flew with 20k miles each for fucking up on our trip last time. So any flight fuck-ups = I call delta and expect free miles.
The problem becomes I fly Delta because I got a poop ton of miles with them, but if its dramatically cheaper to fly with AA or United I fly them as well. So I have all these miles in alll these accounts and I need to keep renewing them. And this here is a good way to renew my AA shit.
Miles are kind of like a game.
Here is the kicker though. I use my fidelity 2% cashback card to pay my delta credit card (and i pay my fidelity card off every month). So I get miles and 2% cashback on allllll my shit.
This is a high-on certified rant.