It's because they're cowards, and they know they're being idiots! :-)

Here' another, better explanation: Jay Kuo today had a nice article on this poll on Substack. He said that the poll is badly administered in a bigly way.

They didn't poll likely voters, they polled registered voters. And the part of their pool of likely voters was badly chosen.

And the way they polled young people is completely the opposite of some other polling:

NYT 30%-31% Trump up 1

Harvard/IOP 56%-37% Biden up 19

Pew 59%-38% Biden up 21

https://statuskuo.substack.com/p/do-better-new-york-times

So it may be that I am not seeing responses because young people just aren't dumb enough to vote for this guy, and there are no such numbskulls reading this blog, lol. :-)