There are several reasons why collectors own duplicate titles (at least temporarily) instead for the purpose of pure "hoarding". This is a legitimate question.
The only time I personally own duplicate games are for restorations, or game trades for other titles, especially rare games. I have done this with Ted Zale games. I know several collectors that have owned up for example 7x Fireballs or 10x Nip-Its and were not pinball brokers which was rediculously excessive. I have to "pry" games out of their hands.
However, It is easier to do duplicate restorations while they are side by side, not just sitting on storage for decades. Bulk deals do happen for identical titles. I just did one for 2x Gators and 1x Alligator, among other games. In some rare cases I buy for "Frankenstein" builds as not all games can always be saved the due to severe damage or missing parts.
The final reason is to protect games from being parted out unecessarily, "scrappers", or simply turned over for profit as a projects or baling wire repairs from "flippers", which is more common than people realize.
I dislike "hoarding" or "pinball scrapping".
I do not throw away good used parts!