This is my opinion ,not based on scientific data / theorem or dubious web links ;
Apple fear making bigger devices with resizable widgets and customisable setup and open development, purely on the basis they know unless they put in all the work or supersize the processor and ram the devices will LAG , and apple simply can't have that , or they will have devices with no distinction from android than better build quality and a certain fruit based imprint on the back
Just my opinion , but think about it, , its either commercial (profit margin / component costs) or pure fear they will have a lot of work to do not to end up like a one horse android (trick) pony.
Not only that but it will kill the battery. Androids come a long way with battery life while keeping functionality.