Masks are supposed to protect others from you. Wearing a mask is not meant to help a person who may be at risk decrease his/her own risk of infection.
In any event, now that spring weather is here in the northern hemisphere and the vaccination campaign has given people hope, social-distancing rules are being flaunted in many countries and at-risk populations may find it hard to properly distance when they leave their homes for e.g. basic shopping. So, since the "other options" don’t always work, keeping up the vaccination campaign is very important to reducing infections.