This is primarily an American issue. Many people lack the access to healthcare and even if you can afford to miss the pay, some people can't afford the doctor's copay, or payment towards deductible. People I know (in the service industry) have been urged by employers to come to work "if it's not too bad"
We do "work" and "healthcare" wrong and no one wants to talk about that.
My wife actually just texted me and this is happening at her office. The owners called the office manager (who is one of about 4 or 5 who actively has COVID) and told her she needed to be up there in the office putting out fires.