Phillips is not getting more press coverage because he's a nobody who isn't polling high. No one expects him to win the nomination. He's got it all backwards.
Did you know Bill Weld ran against Trump in 2020 in the Republican primary? Or Joe Walsh? Or Mark Sanford? Did you even know there was a Republican primary in 2020? The reason you didn't know was because they were all polling in the single digits.
Biden could keel over tomorrow and Dean Phillips would still have zero chance at winning the nomination. If Newsom or Harris challenged Biden for the nomination you know the media would cover it.
If Dean Phillips' chances of unseating an incumbent president are what Silver calls "remote," then we're gonna have to come up with a new term to describe all the shit we normally call "remote" that is infinitely more likely than that.