Comment by pitched

The part that takes time in UI isn’t wiring up components, it’s the small changes like something is a pixel to the right or that gap is two pixels wide. Changing those in a C++ project means recompiling and that adds up to significant overhead over a day of polishing the UI. If C++ was able to get builds out in less than a second, this wouldn’t be an issue. People value performance in their own tools more than the tools of their customer.