Covid spreads far more easily indoors. Breakthrough cases are becoming more common. Group immunity through boosters (or exposure) is more effective at preventing the spread of covid and reduces the chance that any one individual will catch COVID (and continue to spread it).
> Cell-based immunity remains intact without boosters and is key to preventing hospitalization/death.
Source? And further, preventing hospitalization and death is great - but we should aim to do better, preventing sickness, stopping the spread, reducing the chance of mutation etc which is what the vaccines (initial and boosters) enable.
ETA: in another of your comments you cited an article with this conclusion:
"Across the age groups studied, rates of confirmed Covid-19 and severe illness were substantially lower among participants who received a booster dose of the BNT162b2 vaccine than among those who did not."
and still somehow came to the conclusion that not getting boosted is better for society.