I think proms will go by the wayside. Years ago, it was a way to have a more formal gathering for young people.
I see what you mean in one way. The rich used to and perhaps still do have expensive Debutante Balls for their young ladies. I don’t know what the equivalent was for boys, but I’m sure it existed. Now, more that just the upper class can gain access to good jobs, depending on education, presentation, connections and plain old luck.
The proms may continue their popularity primarily because they are often seen as a rite of passage from childhood into adulthood. Almost every teen wants to get older, both girls and boys. With more families being unchurched, there are fewer rites of passage available to kids nowadays that can be recognized as such. For others, getting their own car was and continues to be the point of arriving as an almost adult.
Proms are an anachronism, a throwback to a time when that formal dance represented a young person’s entrance into the adult social world. They should go by the wayside, but they won’t because too many people make lots of money on them.