The feature dates way back to perhaps 2006, per Jetbrains' PDF archive[1]. Jb also updated their structural search UI/UX in 2018[2]. It is possible that users do not buy in the idea of SSR. Alternatively, it may be caused by the fact that Jb SSR's mixed language support. [3][4][5]

[1] https://www.jetbrains.com/idea/docs/ssr.pdf [2] https://www.youtube.com/watch?v=YeGPO-UHTbs [3] https://www.jetbrains.com/help/idea/structural-search-and-re... [4] https://www.jetbrains.com/help/go/structural-search-and-repl... [5] https://www.jetbrains.com/help/pycharm/structural-search-and...