Hi, I was looking at lyrics of the song called "It's a small world" and in the song sheet someone gave me, I saw this line.

It's a world of laughter, a world of tears, It's a world of hopes and a world of fears.

My question is, "Why did the author use 'fears' and 'hopes' and not 'fear' and 'hope'?"

I think because in the context they are used, the use of "fears" and "hopes" is better and gives a more realistic feeling to the song and to use the uncountable and abstract "fear" and "hope" wouldn't be good.

Like here, one could use both the words 'discussion' and 'discussions' but the 'discussions' sounds better in the context it is in (eventhough hard to tell exact context from this sentence).

I have written this article with the questions for you to ponder on to elicit more future discussions on the topics we raised previously.
I think to emphasize the hopes, fears, etc., of many individuals, each person having his or her own set.
I would use the singular discussion if I expected the group to meet, perhaps, only one more time. If I wanted to emphasize the possibility of several meetings, I might use the plural. My tendency is to use the singular always, but I think the plural can't be considered to be wrong.

There is a logical grammatical explanation and has nothing to do with emphasis. When the plural of a noun is used it refers to that noun in general. There are many types of 'fear'. So, all the types are being considered here.