They do have a way to mass harvest them on public lands and land where they can get permission to do so. It doesn’t work in my area because we are too forested here. Basically they chase them with a helicopter and use an AR to shoot them.
Years ago, Pres. GW Bush (before he was President) started a program in Texas to harvest feral hogs, process the meat in USDA slaughterhouses, and use it to feed the homeless. I’m not sure if the program is still ongoing, but it is something that has at least been tried, and one that a lot of people were behind at the time.