I think what makes this a different case from boxing deaths and other sports related deaths is that this type of incident is not a regular part of the sport, albeit a freak accident that falls outside typical play. Should be noted whoever was arrested (pretty obvious who) was only arrested, doesn't seem like they were charged with anything. I wouldn't expect anything to come of this, just seems like they're doing their due diligence and following the legal process.
Nope. It's a pretty divided issue it seems. It's mandatory as a minor, but once you hit a certain level/age it's not mandated. Kind of ridiculous seeing as how I've personally never played without one and never had an issue with wearing it. Some claim it's a nuisance, but I wouldn't particularly take those people very seriously. I could understand players not wanting to wear a mouthguard or a cage, but not wearing a neckguard can be lethal.