Why does the Boeing 787 have fewer cockpit windows?
It is because of the carbon fibre. This is the same reason that the 787 has bigger passenger windows. Here you can find a link explaining the polarized windows on the 787. Because of its higher tensile strength, you can have bigger windows. Windows are considered weak points in the fuselage where there is no structural reinforcement. This means that the windows have to be supported by the fuselage and structural components around the window. Boeing Pilots do not fly with their elbow out the window during flight, so Boeing removes that feature. They added bigger windows because they could. There is there separation for the six windows because there is support needed.

Hope this helps, Charlie