by this I'm sure you mean to imply, we have 3 years of 1st hand accounts of what covid-19 can do to a person.

you don't know how old this person's mom is. you don't know if they have cancer. or an autoimmune condition. or live with their parents. or live with or work with an immunocompromised population. or hell, maybe they just don't want to potentially get sick for life or die?

covid doesn't care how healthy you are. it's not "just a cold or flu" for everyone. yes you should still aim to be healthy and sustain a strong immune system in general, but we know that this doesn't always prevent a terrible and potentially fatal result of a covid-19 infection. if you haven't caught it yet, you don't want to.