Maybe they looked at the advice, looked at the numbers and decided that it's worth taking the risk. Isn't that what personal freedom is about?
The thing is this is not a just a personal risk. Maybe other people who have no choice but to be outside because of their work or st else don't want to take that risk but this risk is being forced on them. Isn't it our responsibility not to increase the risk on their lives if we can stay at home?
Can't you justify banning drinking (think of the children!), driving (you might run someone over!), or pretty-much anything you like using the same argument?