カタカナanalysis

In class, we learned the main occasions in which to use katakana:
a) loan words/foreign names,
b) onomatopoeic expressions, and
c) to add emphasis (though I think sometimes it is hard to distinguish between the two).

Exhibit A: ローシヨンプル（lotion pool, featured in a Japanese game show)
B and C: ピカチュ!
 
check out all the onomatopoeia.


ピカピカ　"Pika Pika" in Japanese means emitting light or brightness, which I found in a japanese adaptation of アカハナのトナカ (Rudolph the red-nosed reindeer). It is said to be onomatopoeic, but it makes more sense to say it's emphatic?

 チュ "chu" is the onomatopoeic expression for the squeaking of a mouse.

My question is why is Reindeer in Katakana if there is a Japanese word for it?
So I searched and multiple online descriptions of Katakana says that it can also be used for:
--> new Japanese words such as カラオケ
--> Scientific words such as ガン (cancer)
--> Fruit and animals, even though they have Kanji, but the kanji is said to be difficult and therefore replaced
--> Manga and anime when someone/something foreign (non-human) is speaking (i.e. alien/robot)
--> in advertisement, to be hip

IN CONCLUSION: I think the textbook sticks to the basics rather than enumerate everything because katakana usage has expanded due to culture/convenience, etc. Possibly too expansive to enumerate everything?