The reason the U.S. lost most of its very early (late 40’s - early 50’s) was due to it’s mostly being broadcast live and only preserved to kinescope, if at all. Besides, kinescope sux.
Then, there was the case of most of the old Dumont shows being dumped in the Hudson…
Super Circus was live, and anything like a telethon for a charity. And of course sports, like the Roller Derby and women’s baseball.
A friend of mine who worked for one of the big networks in the sixties said he went looking for the old tapes and that was what he was told, that they had been used over and over again. He had been thinking he would put the old shows together into a program.