Simple....WTIC-FM is hot AC, music that is already available on popular locals 93.1 and 94.7. Kiss, on the other hand, is straightforward CHR - a format not locally available in Springfield. Comparing them is a bit like comparing oranges and limes; yeah, theres a bit of overlap, but the tastes are quite different.
WZMX does well up there too, for the same reason: it offers a format (CHR/U) not available locally in Springfield.