Altcoins create variety in the crypto world. Each one that is created advances the blockchain and at the same time develops it. So whether they do not have some obvious real or proven use, as long as they develop the technology I am ok with it. They create diversity in your holdings.
Don't agree to it though. I expect profit for each token I hold so if it doesn't really have a use case but I still got it, I will definitely make the initiative to sell them all than keep holding it. There ain't no use if its just for diversity for your holding, those token has to reason why it can have some demands in the market, if it doesn't then it has zero value.