Because it's being prudent. With such a big project, the unknown unknowns are numerous. Something nobody though about lurks in this nogil build, and we are onl

Because it's being prudent. With such a big project, the unknown unknowns are numerous. Something nobody though about lurks in this nogil build, and we are only going to find out when it goes to prod and users report about it. Instead of breaking the entire Python community's code, the risk is opt-in for a few years.