What does it mean exactly when an old show can't/won't go to streaming or DVD because of music rights?

Submitted ⁨⁨1⁩ ⁨hour⁩ ago⁩ by ⁨bOt@zerobytes.monster⁩ to ⁨television@zerobytes.monster⁩

https://www.reddit.com/r/television/comments/1wefdd3/what_does_it_mean_exactly_when_an_old_show/