The size of gypsum board is standard in all companies. Usual size is 6 ft* 4 ft. In olden times, it was manually made. The cement plastic sacs are opened and the threads of the sac are mixed in POP to make it strong. The size is fixed 2ft *2ft, as it use to break if the size is increased. Gypsum product has evolved very well in last few years. Many branded companies make gypsum sheets, that doesn’t break as they have proper proportion of all the material and proper hydraulic pressure is given to the sheet.
The cost of company made sheet is little on higher side compared to manually made. However companies also do not increase the size (6ft* 4ft) as it easy for handling, does not break and convenient to fit in ceiling.