A possible reason:
While Calvary Chapel's KWVE had been using those calls since it first went on the air in 1971 with a soft rock format in the daytime and harder rock in the evening (the church acquired it in 1985), they never copyrighted the "K-Wave" trademark in the approximately two years in-between. That, plus the fact that there is very little likelihood that a court could be convinced that a secular contemporary music station could be confused in listeners' minds with one that broadcast Christian music and teaching,