Chinese is not English. It is a truism, but it bears repeating when a learner mistakenly takes English rules as the "norm" for learning Chinese. Intellectually, it is a fallacy to judge Chinese punctuation by taking the English full stop as "normal", and then on that basis decide that the Chinese 句号 is an exaggeration. It is important to bear in mind that the function of a 句号 (。) is different from the function of a full stop. A full stop is governed by rigid rules of grammar defining what constitutes a complete sentence (and therefore a full stop must be used. There are no such rigid rules in Chinese, in spite of legislative attempts. It might strike you as silly to pass a law to regulate the use of punctuation. The irony is that punctuation marks are much more flexibly used in Chinese in practice than in English. "What constitutes a sentence" is open to subjective judgment in Chinese. A Chinese 句子 is not the same thing as an English sentence. A Chinese 句子 is an idea, not a grammatical structure. It is governed not by a verb and clauses (if any) but by its content and the writer's judgment as to the completeness of that idea. Why is it a small circle? Why not? It is clearer than a dot. That was particularly so when people were writing in ink and a dot could have been mistaken for an accidental drop of ink. A small circle is visibly a consciously written mark. A final word of advice: lay down your English grammar when learning Chinese. 中文不是英文。 这本来是很显浅的道理，但偏偏就有很多人不明白。 Here is a link to a brief history of the Chinese 句号: http://www.pep.com.cn/xiaoyu/jiaoshi/study/jszy/bdfhyf/jh/201012/t20101202_980825.htm

that question is equal " why Chinese use chopsticks, not normal tableware" Chinese use 。many years.

to make it noticeable

It might be related to Chinese being written vertically in the past.

Just want to add on to what others have said. As the others mentioned, the punctuation is generally just different. In Chinese you have the usual ',' but also a '、' for making lists. For titles they use《》instead of quotes, etc... In particular they use “。” less often than we use periods in English, and will often seperate what we would call sentences in English with (splice) commas. Sometimes full paragraphs will be a single sentence.