These cryptocurrencies are very volatile, their value can fluctuate greatly. Many memcoins are created as a joke. Given that they were created as a joke, it is likely that Memcoins will attract scammers who will commit scams. I don’t understand why else they are created, so they often come and go along with the popularity of their meme.
I don't think that you're right. There are some meme coins that gained certain popularity and continues rising and improving. It works the same way like with all the other crypto. If the devs are serious about the project - they will do everything in order to make it grow and gain popularity.