Why is Salah prayed somewhat differently across the world, considering it was an extremely common act

As we know Salah is a daily act for us muslims. But why is it that it is prayed differently though it was an extremely common daily act for the Prophetﷺ. For example: i) Why is there a difference of opinion of wether we should raise our hands (Takbeer) for ruku3 , coming up from ruku3 etc? ii) Again why is binding your hands or not getting up from ruku3 a matter of dispute ? iii)The dispute of wether we should raise and point with out finger while sitting the whole way through, only during the tashahud or only during the shahadah. These were extremely common practices but why are there differences in opinions about them. Please provide your proof using Ahadeeth or trustable sources aswell. Thank you.