I've thought all along that it was important to vaccinate those over 70.
Re protecting others, it's true but don't forget that young people being more resilient could have protected the elderly (once the latter had been vaccinated) through developing immunity through natural infection. This has been demonstated (in Israel recently) to be as good if not better than vaccination immunity.
But if you are relying on natural immunity from infections, firstly there will be a load of those people, however young, who will get seriously ill, some will die and others will have the long lasting effects of long covid. Also you simply cannot generate natural immunity as fast as a vaccination programme without the infection running riot, and when infections run riot you cannot protect the vulnerable as sooner or later the infection gets to them.
Or, of course, you can engage in a highly effective vaccination campaign which will, of course, run alongside natural immunity as until the virus is completely eradicated there will always be some underlying level of infection ongoing.