It's about understanding why Tesla doesn't like Vehicle-to-Grid when it has the brain to allow it:
1) Powerwall sales might be affected
2) Supercharger to Vehicle to Grid arbtrage
3) Wears and Tears.
You need to give Tesla a reason how it will be beneficial for its investors to use its technology to do those 3 above things.
An average US household electricity usage is about
897 kWh per month or 30 kWh per day.
Your long range Model 3 battery pack is about 75 kWh which is more than double an average household can use per day.
Your warranty is 8 years or 120,000 miles.
Your rated range for your battery is 310 miles.
120,000 / 310 miles = 387 complete cycles.
So if Tesla allows Vehicle to Grid option, the worse scenario for Tesla is: you would almost use up all 387 complete cycles in a year that has 365 days. And it's not even 8 years yet and what if you only drive a few hundred miles a year, so it's no where near 120,000 miles to run out of your warranty yet!
That's the wear and tear part that Tesla is not willing to finance you!