There are a number of reasons. Perhaps most importantly, they sabotage
herd immunity, letting the virus rampage through populations that it otherwise wouldn't be able to penetrate.
Y'see, getting infected doesn't just endanger
you. It endangers
everyone around you.
Secondly, you're repeating a rather blatant form of the
Nirvana fallacy, in that no credible source claimed... well, pretty much anything you just listed. Getting jabbed leaves you
comparatively protected, but not fully immune. You can still get sick from COVID (although you're less likely to die or suffer serious after-effects). If
you're driving safely, and properly using your seatbelt, why should you care that other people aren't?
Well, the answer becomes relatively obvious when that drunk driver slams into your car -- or the idiot without a seatbelt goes flying around the car in a crash and breaks your neck with his leg.
(
Not a hypothetical, by the way: This is the actual reason why we have seatbelt laws. I was describing the events of a crash video I had to watch back in college.)
Thirdly, as noted, they're not just influencing their own behavior. Many of these people are discouraging or preventing
other people (e.g. their kids) from getting vaccinated.
Fourthly, as
also noted, antivaxxers tend to also have (and spread)
other dangerous medical beliefs. Over the course of my career, I've had to --
among other things -- try to lobby against an antivaccine-inspired chain of clinics dedicated to chemically castrating children with disabilities, track down a network of antivax parents who were having pig whipworm eggs smuggled in from Thailand so they could deliberately infest their kids with porcine intestinal parasites, and deal with parents who were trying to give their kids "all-natural," "alternative" protection from childhood diseases (measles, mostly -- this was before COVID) by making them drink week-old urine.
This is an incomplete list.
On the more tragic side of things, I've also dealt with parents who refused the
Vitamin K shot at birth (because any injection
obviously has to be a vaccine and they don't want their kid vaccinated against their will) and then had said kid die or suffer permanent brain damage from bleeding... which they then blamed on "stealth vaccines" supposedly given to the kid against their will.
Fifthly, the antivaxxers are,
in fact,
assholes.
Which means jack shit if you're immunocompromised or undergoing chemotherapy. When we talk about people who can't get vaccinated, we're not usually talking about access to the vaccine: We're talking about people who
medically can't get vaccinated.