The problem is when you have a police line established that is 25' from the action and then have to move back another 25'.
I'm not sure exactly why bodycam footage is so much worse. I think part of it might have to do with the odd height it's placed at.
In practice, it's often used less... wholesomely, as you'd expect.
Its the lack of any stabilization. If you twist your body a tiny bit then the focus of the camera moves drastically; this differs from when you're holding a camera far from our body using your arms. When you move your body your arms will counter-act that and the video won't jump as much.
Part of the problem isn't actually refusal to cooperate on the part of police orgs, though. I happen to know second-hand that the companies operating the cameras provide abysmal and overcomplex, failure-prone software and hardware, and storing all that camera footage in a way that is quickly accessible to the public would approach Youtube levels of footprint/operational costs... It's complex, and police orgs, in addition to being resistant to change, are also not exactly known for their technical acumen.