As a thought experiment: send your next email 1 character at a time by regular post.
One doesn't have to do something often for it to be an awful experience. We choose tools, in part, because of the worst case experience not only the average case.
We shouldn’t optimise for the least frequent use case at the expense of the most common use case. Reversing a car is awkward, but we don’t reverse the steering wheel so that you get to turn the right direction while reversing.
Correcting reversed steering only while backing up is entirely possible. Drive by wire allows it.
Car designers realize the user base knows the older UI and uses the older UI without issue. The "install base" of existing user skills is a compelling reason to not change.
One doesn't have to do something often for it to be an awful experience. We choose tools, in part, because of the worst case experience not only the average case.