Why? What value do you see in Peter Doocy asking Kamala Harris what her opinion is about Donald Trump's latest lie? Or his hairdo? When is the last time any White House press reporter asked the president, or his spokesperson, any question that required a longish, thoughtful answer, and (if that actuallly happened) then offered a thoughtful, on-topic follow-up? It doesn't happen.
Neither candidate has been inclined to submit to "traditional" news conferences. The reason, I suspect, is that both campaigns realize that the reporters in such settings aren't interested in anything substantive; they're interested in scoring sound bites, so they can be the reporter who generates mouse clicks/page views, or whose 30-second clip gets on nightly news. This is one of the fallouts of "news as entertainment" that has consumed mainstream media (first the broadcast media, and more recently the print media, as they have become dependent on the internet, rather than the printed page, for revenue).
Long-form sit-down interviews allow the candidates to actually discuss something substantive. Yes, it's better when those long-form interviews are conducted by serious interviewers who are not in the bag for one candidate or another. That happens at least some of the time.
I had to laugh at your "Democratic leaders and their kept media" phrase. If you're referencing MSNBC, you may have a point. But the rest of the mainstream media? What else do you see as "kept media" of the Democrats? The vast majority of the mainstream media is, in my opinion, "kept" - but not by the Democrats; by their corporate owners (not specifically Republican, but interested in low taxes and minimal regulation), who have intimidated reporters and editors (with loss of their jobs), with the result that most of them find it impossible to just report the truth in plain language.