Why does anyone, anywhere, still tweet?

In a span of seconds, Roseanne Barr blew up her life this week, rage-tweeting racist and bigoted commentary.

Just one day later, the Philadelphia 76ers announced they were investigating their team president and general manager Bryan Colangelo amid allegations he operated five secret Twitter accounts to gossip about and gaslight his own players.

In April, leading NFL prospect Josh Allen’s entire future was imperiled hours before the draft when racist tweets he’d posted in high school resurfaced. (After hasty damage control, the Buffalo Bills picked Allen.)

If Instagram is the platform for presenting your fake enviable life and Facebook the hub of virtual friendship, Twitter is the repository of the id — the childish, brutal, needy, raw, unmediated id. It somehow brings out the worst of human nature, yet celebrities, athletes, politicians and journalists still use it.

People who already have public platforms somehow do not find this enough, somehow convinced by Twitter that every thought they have must be so brilliant, so original, it must be shared with the world.

It’s usually not. Just ask Kanye, or his alter-ego Donald Trump.

“I was hacked,” said Anthony Weiner in 2011, denying — before admitting — that he’d tweeted a lewd photo of himself to a 21-year-old college student.

Weiner is now in federal prison for sexting with a 15-year-old girl.

“When a friend found [those posts] in December and sent them to me, I was stunned,” said MSNBC host Joy Reid in April, after homophobic statements on her Twitter feed surfaced. “Frankly, I couldn’t imagine where they’d come from or whose voice that was.”

Sure.

It tells you something when Silicon Valley execs stay off the social media platforms they’ve engineered to manipulate and addict the rest of us. Steve Jobs famously limited screen time for his own children. Evan Williams, co-founder of Twitter, has denied his kids iPads in favor of books. Bill Gates limited screen time for his children and didn’t allow them cell phones until they turned 14.

Twitter itself is only 12 years old. We haven’t even begun to understand the ways in which it’s changing us individually, politically, socially, morally, neurologically. That even the wealthy and powerful can be decimated by one digital utterance should alarm us all.

A 2012 study at Chicago University’s Booth Business School found that Twitter is more addictive than cigarettes, alcohol or caffeine. Participants reported the greatest “self-control failure rates” when it came to checking or posting tweets. In 2014, a study by market research company Neuro Insight found that Twitter users reported that they felt a high degree of “personal relevance” when tweeting — 51 percent, higher than with other social media platforms.

When ABC announced the “Roseanne” reboot in January, Barr herself said she couldn’t be trusted with her own Twitter account and that she’d turned it over to her adult children.

“I didn’t want it to overshadow the show,” she said.

Now Barr has lost millions of dollars: Her critically-acclaimed reboot canceled, re-runs dropped everywhere. Barr is a pariah, someone even Charlie Sheen feels comfortable criticizing — where else? — on Twitter.

“I apologize,” Barr tweeted at 7:28 am on May 29. “I am now leaving Twitter.”

Later that day, she was right back, blaming Ambien. That wasn’t the drug to blame.