It's a trend, a fad, really common with bowling balls. Sometimes its the ball that will hook on soup, sometimes its the most aggressive reactive ball, and so on.
This trend kinda started with the Storm Paradigm and The One. Coverstock technology is getting a lot of spotlight these days. A medium-heavy oil ball can now be a pearl reactive (or highly polished reactive). The One is ridiculously popular and has a ton of backend, which catches a lot of peoples eyes. Now everyone is trying to market a ball like that. Also, these less hook balls are more versatile. Joe Bowler may be starting to see that heavy load particle balls aren't where his money should be going.