I dont know what you mean by "vanishing low", but as of April 26 there had been about 9200 breakthrough infections. Granted, this is a low rate, but certainly not zero, and this was while a mask mandate and social distancing were being enforced. Personally, I dont feel qualified to determine what "the science" is. Nice that you do. Even if one accepts the CDC version of "the science" that it is ok to not wear a mask if vaccinated but to wear one if you are not, that is simply not going to happen. Now we will have the 30 or 40 % still not vaccinated running around on the honor system to wear masks. Absolutely asinine.
Ask yourself what the significance of a "break through" infection is.
What are the vaccines supposed to do?
Vaccination is not supposed to prevent you from ever getting covid. The efficacy is based on prevention of the most serious outcomes, ie hospitalizations and death.
Yes, you may get covid. You may get sick even. You may feel like shit and take a few sick days. But you won't die.
Unvaccinated are not a serious threat to you. It's more the reverse. If they engage in dangerous behavior, that's their choice.
We never mandated masks and all these other measures for previous respiratory diseases, and they did kill 10's of thousands of people a year (eg Flu.)
You are free to wear a mask, but continuing to mandate masks once the threat level has been mitigated would be a new national policy which CDC isn't recommending. Target has never been zero.