Why do historians find periodization useful for the study of history?

Since humans tend to go through changes in periods over decades, and even centuries, it often makes little sense to give exact dates for every single instance of events. It is also a way for historians to put a general time period on an event. For example, we know that bronze became a product a long time ago, but we define its height of use during the Bronze Age. It helps generalize the 8,000 years of recorded history that historians sort through.

the catholic church withhold people's access to the bible during the middle ages.

people could go to church and listen to the teachings, but it was absolutely forbidden to own and/or read the books of both the old and new testaments. it was also prohibited to translate the books (which where originally in biblical hebrew) to any other language.

this was done so the church could remain in control of what their teachings were and to enhance their importance and power, while also being able to judge people's actions through information that was unavailable for the general public.

food chain i would say only because there is competition on getting food and survival