Any unnecessary contact with other people risks unnecessary spread, illness and death.
Hospital visit, or working in a hospital? Necessary.
School contacts? Generally considered necessary.
Shopping for food? Necessary.
Shopping for the right colour tree lights, meeting friends, going out to watch fireworks in a crowd- unnecessary and contributing to extra deaths. Put a
CV+ asymptomatic person in an empty room, and they won't infect anyone. Add a few other people who also need to be there, and they may infect a few people. Add a load of extra people who don't need to be there and everyone gets crowded together and more people will get ill.
Going out increases other people's chances of getting it, as well as your own.