On-full departure is easy and convenient - a new transportation paradigm

Many requirements for a rationalized transportation system are eagerly discussed, but one that is always ignored is the traveling of large buses and trains with hardly any passengers. This is obviously a waste of energy in many ways. This is called on-time departure. But there is a critical example of another way of organizing transportation that I call ON-FULL departure. I used it when I lived in Turkey, it was wonderful, and I miss it. Why can't we organize something like that here? And what makes Americans so resistant to new, logical ideas unless those are a product they can use directly?