Satellite communications, point-to-point microwave systems, and other similar things (high-data-rate, point-to-point communication) all operate near this band. However, there's plenty of spectrum and the use cases may be declining. There were also some radar systems in this band, but IIRC the useful new radar systems are higher-frequency (10's of GHz for resolution) or lower-frequency (10's-100's of MHz to have longer range).