i think this user is very new to BIM,
but i hope i can give you some of the concept.
in fact, in my point of view,
the aim of BIM is to let our computer to know the model instead of the 3D model before which only give us to visualize the space, and the computer only know that the model is only boxes with some kind of mapping.
in our traditional 2D and 3D CAD,
what we have is only some digital pen with unlimited paper space which computer can not help us much.
all the works was done manually when BIM was not there, also, the accuracy, productivity is not good because the drawings are drawn, checked by our human eyes. most of the software was not well design specifically for construction.
now, BIM makes good use of computer for constructions. and i think BIM will be the future standard.
p.s. you may find out more answer in the internet!!