Secondly, and this one applied to me: given how new the vaccine is, and the slight chance of heart inflammation and blood clotting among other things, many people would rather passively get COVID through no fault of their own, and very likely recover from it easily like most, rather than purposefully get a shot which means they’re directly playing a role in, in their mind, potentially bringing harm to themselves.
I waited 8 months of general availability of the vax, and then I was comfortable enough with the (lack of) side effects to overcome fear #2.