" The Fugitive" case was a huge blunder, to be sure. (I'm not familiar with "My Three Sons," but I assume it's something similar?) But the thing with "The Fugitive" is it came from miscommunications, legal timidity, and outright mistakes. I'm not defending it -- they blew it, big time. But one thing that did not cause it was laziness! That's my point. Replacing all that music was a stupid thing to do, but also a lot of effort on the part of many people.
I have a friend who rescored a bunch of '80s television series, replacing songs with his own score. His hiring was not the result of laziness. The studio (I won't name it) simply felt they could not afford to license the songs (and yes, they had priced them, and kept one or two of the less expensive ones). You can say they were cheap, or merely pragmatic. They definitely were motivated by financial concerns, of that there's no doubt. But again, they were not lazy in any way. My friend's services came (relatively) cheap, but each episode had to be respotted, laid down, and mixed from scratch. You can bemoan the music replacement all you want, and that's your right. But if you claim they didn't try to license the music, or didn't bother, you'd be wrong.