A lot of focus on covid for younger people is on mortality but not enough on morbidity,If we accept those under 40 are at a very low risk I still don't know that these hold up.
Protect family & friends? - They're vaccinated.
Avoid health difficulties - Very slim risk (All vaccines carry SOME risk)
Halting of the spread - Numbers are already lowering, if all those previously mentioned are vaccinated then that halts the spread. Let alone those already previously infected.
Risk of fatality under 40 - VERY VERY VERY few without comorbidities have died from Covid.
My wife's cousin is early 30s, ran marathons, never unwell. he was on of the first people hospitalised in ITU with covid around March. He was discharged after a long time on ventilation after 3 unsuccessful attempts to extubate. Because of the high sedation, he has chronic insomnia, tiredness, chest pains, shortness of breath on minimal exertion, persistent sore throat.
We don't know the long term effect of covid yet fully - we know it can cause heart problems in a significant amount of people, even young. But I know many who contracted covid and had mild-to-moderate symptoms yet have debilitating symptoms from chest pains, shortness of breath, chronic cough, vertigo, depression, rashes with little improvement from traditional medication regimens that we use to treat aforementioned symptoms.
And we don't know the even long term sequelae of this virus - as mentioned we know other viruses can have significant long term effects such as cancer (e.g. HPV), irreversible neurological disease (e.g. SSPE from measles, multiple sclerosis from EBV), chronic pain (post-herpetic neuralgia from varicella zoster virus).
Bottom line, if you contract covid you probably will be fine, but there is a significant chance that you won't be.
I don't know when I'll get the vaccine but I'd do everything I can do get it personally.