Why is late-night radio hundreds of percent better than drive-time radio?

In drive-time you've got Wogan's grating morning silliness, Shaun Rafferty creeping up to random classical musicians, or Johnny Walker, who tries hard but is really hampered by all the traffic news, business news, celebrity guests and guessing games he has to accomodate. But late at night you've got glorious stuff like Late Junction, or Bob Harris on Saturday night. Even the annoying Janice Long was cranking out one belting song after another at 12:30 this morning. My guess is that the corporate reins are slackened for late-night radio - "Play what you like, no-one's listening anyway." So under cover of darkness the enthusiasts take over the airwaves, playing the music they actually love, rather than what's on the BBC playlist.