Like Matt said this is just #churning for sign up bonuses/miles. 
Show me an incentive and I’ll show you an outcome. 
Most sign up for a year, meet the minimum spend, get bonus, then downgrade/cancel when the Annual Fee comes up the following year. 
They do not carry a balance if they know what they’re doing, and there’s a lot of wasteful “manufactured spending” (think buying rolls of quarters with a card then depositing them back into a bank, gift cards, etc)

I haven’t paid for a flight with money since 2015 when I learned about it. Not for everyone though.. 

 congrats. You got yourself a low-paid job.
Courtesy of @jimmysong

https://bitcoinmagazine.com/culture/bitcoin-songsheet-airline-miles

 

 I maybe open 1 card per year if the bonus is good enough to pay for a round of flights for my family. Wouldn’t really call it a job- if I did I wouldn’t mind making $500-1000/hr while bleeding cc companies. 
Otherwise I use cash and Bitcoin. 
No need to be condescending 

 Yeah, I have been doing the same. Use the new card for gas, groceries, bills, never carry a balance and get a free vacation for the family (ok, depending on the card you might need to pay $100-300 for a one time annual fee).
Most minimum spend is really easy to achieve so you never buy extra stuff to hit the target.