It is what it is. As already been mentioned, WWTX would need to buy some land and have a number of directional towers to be able to serve Newark at night. Not worth the money, time, and hassle.
However, I do believe the U of Del FM station WVUD 91.3 also airs the U of Del games (definitely football, not sure about basketball) so any night games the folks in Newark wouldn't need 1290. Granted the WVUD announcers are students and may not be of the same quality as the WWTX sportscasters, but they get to still hear the game.
As CC owns the station and uses it to carry primarily their Fox Sports Radio programming via Premiere Radio [Dan Patrick and Jay Mohr for example], their main interest is in clearing the Wilmington market for their national spots [possibly consider during the daylight hours that some of Philly too, so they may even be selling it as clearing both Wilmington AND Philly during the day]. The local sports programs on 1290 bring in local spots and make CC additional money.
I believe for the U of Del Women's Sweet 16 game Saturday at noon against Kentucky, will be carried on both 1290 WWTX and their sister station 94.7 WDSD, and yes 91.3 WVUD.