Simple answer, because no one genuinely has zero high risk individuals in their day to day, even if it's not someone you know personally. Or even if you don't, your server/bartender/clerk/etc. that doesn't have a choice about being at work very well may.
I'm not saying don't go do anything, but exercising just a bit of caution isn't hard.
I'm not saying don't go do anything, but exercising just a bit of caution isn't hard.