I think its mostly as was already stated. Until Japanese knives became popular...western handles were the only choices, and if it didn't have a full tang, it was probably going to be a pretty crappy knife. The 'full tang' thing has stuck around, even though its not necessary...and with it the preference for western handles in most production kitchens.
To illustrate the fact...I've had a number of facebook friends who go to or have gone to culinary school. When they saw my first kitchen knives...their first reaction was 'wow...nice blades, but...why no full tang??'.
Its ingrained in them.
On the balance issue...I think that's not a relevant point unless you're using light weight traditional or unstabilized handle materials. Every one of my stabilized wa handles I've made tips the scale at around 80g, and I've struggled with getting the balance past the choil on the knives they go to, lol. It almost invariably ends up at or just forward of the ferrule.