Warner doesn't do incomplete season releases and if even one episode has clearance issues, they won't put the season out. An example of this is Cain's Hundred. Warner had the show up on their streaming site, minus the episode Blues for a Junkman, with Dorothy Dandridge singing, which was...
I don't know what the issues are with Colt 45. Warner did a good job of getting their other westerns out there on TV and DVD so there must be something big holding it up, whether its music, underlying rights or maybe an elements issue, although I kind of doubt that. May be something silly which...
Another reason is that all of those shows had very little syndication after the 1960s and the main age of the people who fondly remember those shows is 70+, not exactly the prime DVD sales age.
Music, Music, Music. Every one of the WB detective shows was chock full of music and nightclub scenes, especially Hawaiian Eye, which had Connie belting out numbers in just about every episode. All of those songs have to be paid for and cleared and there is just not enough of a market for 60+...