"Sounds of Silence" Was Just A Song Title, Not A Suggestion

On more than a couple of albums I've bought, the final track will consist of a song, then a long stretch of silence, and then another, "hidden" song. The length of the silence varies, from two minutes up to seven on some of them.

I usually listen to music when I'm driving, so it isn't the worst thing, except that I put the album in to listen to music. If I wanted silence, I could have put nothing in and kept the radio off. Mostly, though, I'm just curious at the logic behind it. Is it a tradition going back to live performances, the performers seemingly leaving or being finished, then starting up again to the delight of the remaining crowd? A special reward for sticking around until the very end? It doesn't require any effort on my part, all I have to do is keep driving and letting the album play. It's oddly placed for an intermission, which I've also seen on several albums. Little bits that are under a minute, maybe a conversation or bit of music, but those are normally somewhere in the middle, and there's still something going on during them