According to the CDC and explained by this article in The New York Times, fully vaccinated people are able to safely go without masks in public, which seemed like a sudden decision leaving many asking, "why now?"
Since the various variants of the COVID-19 vaccine have been out for months now, it is clear that they are powerful in protecting people from multiple strains of the virus. And if people do still contract COVID-19 while vaccinated, it is extremely unlikely they will get seriously ill or be hospitalized.
The Pfizer and Moderna vaccines are 94% effective in preventing symptomatic illness in those who are fully vaccinated, and the Johnson & Johnson vaccine is 72% effective, according to the CDC.
Another concern among many has been about vaccinated people spreading it to those who are unvaccinated. This has been proven to be extremely unlikely, as well. Although unvaccinated people are still encouraged to wear their masks and stay away from crowds.
Essentially, the CDC is rewarding those who have been vaccinated while encouraging those who haven't been to go their vaccines so they can go mask-free, as well. This could cause concerns in public spaces because it fully relies on the honor system.