The problem is that they are opening up too soon. Many countries have cancelled the mask mandate, removing most measures in public places like restaurants, schools, shopping malls and stadiums etc. Most of them got vaccinated, which has effectively prevented serious cases and hospitalizations.
Just like the seasonal flu vaccine, boosting is the first line of defense. When you have enough antibodies in your body, you can effectively neutralize most viruses in your body. This prevents you from getting a more serious case of infection.
You can get tested every day, but you can get infected the next day. But if get boosted, you will get a couple of months of protection.