There is an epidemic of breathy, soft singing in jazz (and some other styles), often without vibrato. The assumption is that this kind of sound is somehow “sexy” or intimate or appealing.
What appeals to us in a voice is its richness or character. We like harmonics. Soft breathy singing has little of that in it. It’s hard to recognize one voice from another.
Think about it: when, in life, do people use a soft breathy voice? In the bedroom (OK), in a theater while watching the show, when telling a secret, when they are sick. The many other circumstances in life cause us to respond with a wide range of sounds, all of which can be part of singing when dealt with properly. People who have only soft breathy sound to offer often get boring very quickly, unless they have a very powerful message to convey that might supersede their sound. If, however, we are moved by the uniqueness of each individual’s voice, that uniqueness disappears when the sound is always only breathy and soft.
Vibrato, too, has gotten a bad reputation. It’s as if musicians think of it as something phony or put on. Nothing could be further from the truth. In a well-balanced, freely produced sound, in a person who has the capacity to sing vigorously, vibrato arises by itself (even if the person starts out without one) and is a reflection of the dynamism of the sound. Most people can learn to keep it out (sing a straight tone) without any negative repercussions. Suppressing it, however, is a way to stiffen the vocal muscles and over time, that does have some negative consequences, particularly in terms of freedom and expressivity.
Just as it isn’t necessary to bellow at the loudest volumes all the time, neither is it a good idea to choose to sing at a low volume without any clarity of tone all the time. Neither shows the voice off to its best advantage and neither will help the vocalist communicate best. If you are someone who sings in a soft, light breathy sound as your “signature sound” you should question why you are content with only that. There is much more available, so don’t be a pseudo singer!