You just answered your own question, they're meme coins they dont need to have any usage or purpose they're just made for "fun".
Anyone can make up coins but why is anyone even buying any of these? If dogecoin has no real use... then none of those other coins have any use. So why do these new coins keep showing up?
Easy and fast money.Everybody these days want to find the next doge or shiba so they invest money on these shitcoins to hopefully hit the jackpot on one of them.