A lot of people here are claiming something "like this is a problem that only affects these idiots". Sadly, that's not the case. A number of these vaccines are only roughly 80% effective. The efficacy of these lies in herd immunity, where the 20% of people who did get the vaccine, but are not protected, will never encounter the disease because the other 80% can't get it to spread it to them.
Let's say you need 70% of people to be protected to maintain herd immunity. Then just 10% of the population needs to be idiots, and the disease spreads to the 30% that isn't protected. Of that 30%, 20 points are people who were not idiots and got vaccinated, but unfortunately are not protected. The idiots will get sick, but twice as many not-idiots will get sick too. Unfortunately, for some of these diseases, the idiots will be hurting many more people than themselves.
The affected people are not necessarily immunocompromised. For example, after two doses of the mumps vaccine, 88% of people are immune. Immunity decreases with time, so the proportion that's immune is lower than that. Let's guess at 80%. You, the person reading this, can be a normal healthy person who got the mumps vaccine, and you have a 1 in 5 chance that you're not immune. Those are some pretty big odds.
Well, I wasn't even considering them. That's a particularly vulnerable group, but I was referring to uncompromised people for whom the vaccine is not effective, or for whom immunity has waned.