Vaccinating everyone, including the young and those who’ll likely be unaffected, is concentrating on those at risk.
The more people vaccinated, the less of the virus there is in the population because fewer people will spread the virus, fewer people will contract it, those that do contract it will have a smaller viral load and therefore be spreading a smaller viral load. Therefore, those at risk are more protected the more people have the vaccine.
Being vaccinated isn’t just about protecting yourself/individuals, it’s about protecting the population. That’s why it’s selfish not to have it.