Here’s my theory, because I’m out and about and doing EMS too. I’m constantly getting low level exposure which keeps boosting me back up.
I guess I could have been out and about all carefree, and then have been the vector to pass it on to my immune-challenged grad student or immune-challenged neighbor in her 80s or my parents in their 80s, or my wife’s mom in her 90s, or etc. To be the vector that led to their sickness or death. But that would have been a selfish, dick move, obviously.
As for the folks who have no fear of Covid and live their life freely, check with an ICU nurse. The vast majority of the ones who are in the hospital express regret at not getting the vaccine prior to getting intubated on their way to the morgue.