Saying you do not care is easy. Living without concern is nearly impossible. Modern psychology makes a clear distinction between defensive apathy and intentional acceptance. When someone habitually repeats the phrase as a reflexive defense, clinicians often identify it as avoidant coping. It can be a way to distance oneself from real hurt before vulnerability invites rejection.
The cultural appetite for the sentiment shifted radically after 2016. That year, author Mark Manson published The Subtle Art of Not Giving a F*ck, which remained on the New York Times Best Seller list for more than 280 weeks and sold over 15 million copies worldwide. Manson's core thesis was not that people should become detached sociopaths. Instead, he argued that human beings have a finite reserve of energy and attention. Not caring about trivial slights allows someone to reserve focus for things that actually carry moral weight.
This perspective borrows directly from ancient Hellenistic philosophy. Epictetus, the Greek Stoic philosopher who lived in the first and second centuries, wrote extensively in his Enchiridion about separating events into things within human control and things outside of it. When someone online responds to an absurd workplace demand or a bad-faith digital argument with "idgaf," they are rarely practicing pure apathy. They are enacting a crude form of stoic triage.