The driving force is money (faster assembly time). Plus all quill stems made became, if not obsolete, useless for new bikes when 1 1/8" steerers came about. Many people leave their steerers long because they are either lazy or afraid to make the cut, they are unsure what length they want or value having vertical adjust-ability (a plus of the old quill stems - properly grease, changing height takes about two minutes)

Some of us consider the proper height of our handlebars a moving target. I vary mine for different rides and different fitness; something I have been doing for 40 years.

Ben