The problem starts in flight schools, and has many elements
1) The vast majority of instructors have no real world operational experience and thus have no idea of operational efficency. There is no penalty in flight training for wasting a bunch of time doing long elaborate checklists, in fact the longer the student takes the more the school makes.
2) Flight schools tend to use the checklist as a training tool loading it up with operating procedures and non essential bumpf instead of only including items directly affecting flight safety.
3) Flight schools in general do not understand the difference between check lists and do lists and the concept of building the checklist around a system of simple consistant flows. Instead every check seems to require a long labourous head down reading and doing exercise.
It is not malice it is just ignorance on the part of flight intructors....and will never change unless there is a critical mass of instructors with some real world line flying experience. Unfortunately the economics of flight instruction in North America will never allow this.