I told you why.
You want to draw a nice bright line. Vaccinated to the left. Previously infected to the left. No immunity to the right. Now we have neatly divided the population into those who are protected and those who chose their risk.
The real world is not that clean. About 2-2.5% of the population us immuno-compromised. Even after they get boosted, they still have one foot on each side of your line. Some people are old enough that they are vulnerable anyway. Even after you draw your neat little line, there are still millions of vulnerable people who don’t really fit on either side.
Then think about what happens to our medical system when millions of unvaccinated people get the new variant, all at the same time? When the lung specialist is working 60 hour weeks treating covid patients, how much time does a pneumonia or emphysema patient get?
It is much simpler if we all follow the advice we have been given: vaccine, mask, outdoor, distance. All of it. Not skipping the mask part because we think a twitter feed does better science than NIH.