My ( simple ) understanding is that vaccines don't stop anyone from getting covid . You just don't get it so badly that you would have to be hospitalized or even die . Like the common cold it will be around for ever , most likely.
So people who have been vaccinated can still get it and pass it on to someone who hasn't yet been vaccinated.
Masks don't protect the wearer , they make a , yes not fully efficient , barrier to what we breathe out .
So until as many people as possible have been immunised the current safety measures are still necessary.
Jan