I would say because it does not appear to be a well-informed decision, but one that stems from "I want to do it my way."
Here is the history of vaccines and their unintended side effects:
https://www.chop.edu/news/long-term-side-effects-covid-19-vaccine
And with these side effects that occurred? You're at better odds getting cancer twenty-two times from an X-Ray, first.
Of all the vaccines, nothing went out beyond 2 months for side effects.
Upon my reflection, and what I learned about how vaccines and the body works when I took clinical anatomy and physiology courses, I realized... For there to be long lasting side effects from a vaccine, there is no way in hell it would spontaneously mutate months, even years later. Cells aren't timebombs. Cells don't wait to evolve, they evolve as soon and as fast as they can.
Hell, the "vaccine" (inert virus) doesn't even stay in your body. The vaccine part is basically your body recognizing the DNA of the Coronavirus. It then attacks those cells that have that DNA sequence.
Now, if for instance, something like that were to happen. Anything that would result from it would have happened to people already in the forum of an autoimmune reaction where their body would literally destroy them as it saw the human body have the same DNA as COVID. This is a callback to "The vaccine will change your DNA." Which mind you, that statement is so intentionally ambiguous that most people who read that see this and take the alarmist approach and think there's some drastic change to their DNA.
But guess what?
The human genome contains billions of pieces of information and around 22,000 genes, but not all of it is, strictly speaking, human. Eight percent of our DNA consists of remnants of ancient viruses, and another 40 percent is made up of repetitive strings of genetic letters that is also thought to have a viral origin.
48% viral origin.
You think this new virus is going to change you dramatically? No.
Besides, the FDA and the CDC have approved this vaccine. And there is nothing wrong with the Emergency Approval. At this point, it's the same as the original approval.