Why isn't In the Heat of the Night available on DVD?

[TMC]

There is no Complete DVD Set of In the Heat of the Night, the TV show,
available on Amazon. Is there some problem in the rights?

There is a "Collector's Edition", but it is missing some episodes because:

"Please note: the following episodes are not included in this
Collector's Edition due to clearance issues: Brotherly Love,
Shine On Sparta Moon,The Family Secret, The Hammer and the
Glove, A Trip Upstate, Intruders, Sister Sister, Walkout,
Fairest of them All, Crackdown, Anniversary, King's Ransom,
A Loss of Innocence, Home is Where the Heart Is,
Indiscretions, Citizen Trundle Part 1 and Part 2, Sweet,
Sweet Blues, Sanctuary, Law On Trial, Singin' The Blues,
Every Man's Family, Maybelle Returns, Ches and the Grand
Lady, Dangerous Engagement, Random's Child."

There are also separate season DVDs (in split volumes) such as Season 5, but it does have some missing episodes:

"Due to clearance issues, the following episodes have been
excluded from Season 5: Sweet, Sweet Blues, Sanctuary,
Law On Trial"