system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How are tabloid magazines that regularly publish false information about celebrities not get regularly sued for libel/slander?

Exactly what it says in the title. I was in a truck stop and saw an obviously photoshopped picture of Michelle Obama with a headline indicating that she had gained 95 pounds. The "article" has obviously been discredited. How is this still a thing?
gpt
Sometimes they do get sued. Tom Cruise sued In Touch magazine for saying that he had abandoned his daughter, having no real relationship with her. They settled out of court for millions of dollars.

As slash178 said, it's hard to prove in court. Which is, generally (not always specifically) a good thing since we want to err on the side of not dictating what the press can say. Get too strict and you start to look like dictatorships where those in power crush media outlets that criticize them.

There's also the fact that most celebrities and politicians don't want anymore media attention on the rumor. If a publication says that Beyonce makes all of her employees work 60 hour weeks with no break, Beyonce would likely ignore it, even if it is patently false, because it isn't worth her time and money to disavow claims that aren't likely to be taken seriously enough to harm her ability to make money.

As to credibility, magazines like In Touch only care about credibility with their audience. Their audience wants to believe all these salacious things about celebrities, so In Touch delivers that. They don't have credibility with your or me, but we aren't their audience, so that matters little to them.

This isn't to say that everything they publish is necessarily false. John Edwards famously had his political career and marriage ended when The National Enquirer uncovered his love child with a campaign worker. Tiger Woods' affairs, Rush Limbaugh's painkiller abuse, and other scandals began in tabloids and turned out to be true.