A Fox News spokesperson tells Deadline the tagline hasn't been used in external marketing or on-air promos since August, adding, "the shift had nothing to do with programing or editorial decisions". The reason the network doesn't want to use the tagline anymore in advertising is that it is too associated with former network chief Roger Ailes, who was ousted past year in the wake of sexual harassment allegations.
In other words, it isn't that Fox News changed its mind about "Fair & Balanced".
You can't call Fox News "fair and balanced" anymore... because they're not calling themselves that anymore. "You Decide" and "The Most Powerful Name in News". It was also instrumental in obfuscating the network's right-leaning agenda, a goal Ailes admitted to in multiple interviews during his life.
The slogan was used by Fox since its launch, with the tagline reportedly being coined by Ailes himself.
At the time, Ailes wanted to establish a clear divide between Fox News and the "establishment" media, most notably The New York Times. The decision was made last August after Ailes's ouster by Fox News co-president Jack Abernethy, because the phrase had "been mocked", one insider said. "Like I have every night since I took over from @brithume 8 1/2 yrs ago", Baier said on Twitter when asked if he would change his sign off.
It might seem odd for the network to suddenly care that its venerable slogan is widely mocked, after so many years of emphatically not caring.
Fox News has never been fair and balanced.