The next court date has been set for February 21.
https://www.cnn.com/2024/12/23/us/luigi-mangione-arraignment-new-york/index.html
As much as I'd like to believe it's a conspiracy, news organizations make money from clicks. There isn't much for them to monetize between now and February 21, so they're focusing on more immediate stuff.
If they can get good photos and text from the next court date, Luigi will get more coverage.
Edit: there have been like five plane crashes, one US inauguration, and major US wildfires since his last court date.