They only work in that capacity if you already watch a lot of memes, so they effectively act as a shibboleth (in-group out-group separator) for separating people who spend a lot of time on reddit from those that don't.
They still help a lot to keep the audience alerted as long as they are funny or surprising without meta information. Adding "Confused Nick Young" to underline, well, how confusing some features are, will still be understood perfectly well by those who see it the first time. On the other hand, memes like "Scumbag Steve" [2] are indeed problematic, because there is no way to understand the point the author wants to make without prior knowledge.
