It’s certainly not a waste of the taxpayers’ money. Mints make a fortune on selling these coins to collectors.
Collector coins are also loved by governments. Collectors pay a considerable mark-up over face value for the coins and promptly remove them from circulation. Most never return to circulation; because their value to collectors greatly exceeds their face value. Governments can thus, quite literally, mint money; without any risk of creating inflation or triggering a devaluation. The collectors are, in effect, making a donation to the government. In return, collectors get to keep coins they will never spend.
True, which is why I find it surprising the Bureau of Engraving and Printing has not done a series using the one or two dollar bill. I also question why the mint has never done a series of vice president coins.