The safety reasons are actually valid. You can not safely turn off a power-topology with a N-to-N setup. The providers just cant life without that power..
"Protectionist reasons" sounds nice to people who already hate big corporations, but it doesn't make a lot of sense. When the grid is down, it's down. There is no revenue to protect at that point. The actual thing they might want to protect against is big solar farms competing away revenue from fossil fuel plants, but as you'll notice such solar farms are entirely legal.
You need a special inverter for it to not blow up when the grid is running, and even the cheap $80 grid tie inverters on amazon do this sort of checking before activating.
<yawn> This argument again? People have been saying the same thing about backup generators forever and it's just not true in practice.
From the POV of your solar or generator the resistance of the neighborhood is basically a short. Breakers will pop if generator and/or or voltage will collapse if solar. If you are out of sync and the grid comes back your hardware will be what leaves the chat, not the grid's
Linesmen are trained to ground their work first because the far bigger hazard to them is miscommunication among upstream coworkers. Better to liquify fuses or hardware than people when that happens.
If "everyone" had solar or a back fed generator it could be a problem but we'll cross that bridge when we get to it. And that bridge would be crossed procedurally on the utility/linesman side (grounding your work mostly already does but more would likely be desired). They're not stupid. They're not gonna trust their lives to the assumption that the hardware upstream and downstream is going to do what they expect.
>"Protectionist reasons" sounds nice to people who already hate big corporations, but it doesn't make a lot of sense. When the grid is down, it's down. There is no revenue to protect at that point. The actual thing they might want to protect against is big solar farms competing away revenue from fossil fuel plants, but as you'll notice such solar farms are entirely legal.
The protectionist angle is that if generation was more local rather than regional there would be much more competition because it would become more economically realistic for municipalities to strike out on their own and/or parter with each other and do so in order to shake off existing overpriced or incompetent utilities.