Candidate and campaign showing confidence that they can win, instead of going along with the media circus and doing "polls-based decision-making" to publicly signal they might exit the race is egotistical? Right... I don't think it would be great precedent to have a candidate step aside because the pundit and donor class insist on that happening because that group decided to collectively crap their pants.
As someone on twitter put it, politics isn't looking at numbers and knowing what will happen. It's looking at the numbers and then working to make things happen. Biden is doing the work - he's out there campaigning every day, despite the bad debate performance and the media whirlwind that came for him. We can't just run poll after poll to magic up a new candidate pair (eg, Harris + someone else) that somehow polls better and call it a day.