You raise an interesting question, and after reading some detailed discussions, it seems that while there are signs of overlap, a full merger between prediction markets and iGaming is unlikely anytime soon. I found
https://teachingbd24.com/prediction-markets/ which explains that these industries appeal to different audiences and face distinct regulatory challenges. Prediction markets often blend gambling with finance and cryptocurrency elements, and in various places including the US, many event contracts are treated like derivatives by the federal government, adding complexity. On the flip side, online casino betting revolves around games of chance and remains legally restricted in most states except a few where real-money play is allowed. Even though the marketing and product strategies of these industries are converging somewhat, they maintain separate cores. So, while they might share technologies and customer acquisition methods, their fundamental differences in regulation and product nature keep them apart for now.