What do you mean by modules, exactly? In a smartphone, which is the largest market, and where Mediatek is pretty strong, many of those functions are integrated as part of a system on chip. Power consumption also required good interplay between the various subsystems. So it's relatively tightly integrated. You also must have good Android drivers/BSP. And phone vendors are not that interested in changing vendors alle the time. There are also a bunch of patents that one must license, which Mediatek likely already does. Often cross licensing with what is typically competitors (like Qualcomm, maybe even Apple), which takes a bunch of time to set up.