"criticising the use of head voice is like criticising a violin for not being a cello."
Bonnie, I like that line.

We are all born with the physical potential and also limitations of the shape and size of our vocal cords and the unique sound our body can make.

The column of air is a very important fact when it comes to being able to project a voice. If you don't have enough control over breathing in enough air and then controlling how you breathe it out while you sing, then you get that weak, babyish volume. Some people can naturally get some good breath support, but good training will always give you technique that will preserve your voice longer.

Richard, you say you want to know why. I think it is just a fad that has been promoted now and the public has latched on to it as something they will buy. The singer Jewel comes to my mind when I think of a very affected voice. Producers are not experts in voice technique. They will promote whatever gimmick sells.

To understand the transition, known as "passagio" between chest and head voice, google "passagio". Wikipedia and vocal sites will explain it. All singers have a passagio between the resonance that is lower in the chest and the resonance higher in the face mask. With good training, you learn to make a smooth transition so it doesn't sound like a break.

Both male and female voices have a passagio.

Alice in Montana