The issue is that young people can die of covid, even if it's rare, also they can have some comorbidity that they do not want their employer to know about.

Also, you can transmit covid and be asymptomatic.

Finally, death is not the only "bad" outcome of covid. About 1/10 people have "long covid", ie symptoms that persist over time (lack of smell or taste, fatigue..). And this affects young people too.

So, as others have said many times, this vaccine is not a matter of individual choice. This is an infectious disease, so by being infectious, you may harm others, even young people. This is why governments or companies are making it mandatory.