You can trade it with other people, you can create contracts and derivatives involving it. What you can't do is ever get anything of value from holding the stock itself.
This is easy to value, but some people are uncomfortable with the answer. With so much hype and magical thinking, it feels like there most be something meaningful behind it. Repeat it enough and the dogma gradually becomes a truth you can build anything on top of.
And since the company is already bankrupt and all the assets are stripped, it is immune to news that will force the traders to reevaluate and dispel the illusion. The company can't go any more bankrupt, so the traders are looking around at each other and seeing everyone else continuing to trade thousands of dollars for shares of nothing, so they shrug and think "if someone paid a thousand dollars for this today, they will probably be willing to do so tomorrow as well".