They make money off the stories, so... they'll keep coming.
Not least of all, also, they want to use the murders to push their agendas of stealing people's rights away from them. Even though the difference in deaths, essentially, would be statistically insignificant.
Yes, "if one life is saved it's worth it" and all that but we are talking about like 100 lives a year in a nation of 350 million. No other laws in history get passed over such slim margins. Not seat belt laws, bike helmet laws, environmental or pollution regulation, nothing.
*Note, I'm not saying there's 100 gun deaths in the country every year, I'm saying banning the AR to stop these mall and school shootings would save, maybe, that many lives, given that most of these sickos will just use knives or cars or do something else crazy, and that handguns, which will never be illegal, will continue to account for the vast, vast, vast majority of gun deaths.