Its one of those little unspoken secrets. It’s probably right up there with publicly discussion your salary, an ex-spouse, or venereal disease. Very few people publicly acknowledge making use of coaching.
My expectation is that many fear it will reflect negatively upon them. If you’re a senior leader, perhaps there is fear that to admit coaching is to admit a weakness. Of course, in highly competitive environments, such as in C-suite, it might also be viewed as a competitive secret!