I remember the '70s and '80s well, as I grew up in the '70s and remember seeing older console TVs from the '50s-'60s that were still in use. When these sets finally developed serious problems (such as a bad flyback, power transformer, CRT, etc.), they were put out for the trash and replaced with smaller sets, usually 19" portables. The owners usually held on to the older sets for years or decades, even if the TV went bad (they would then use the stereo, which in many cases still worked quite well). The old set was often moved down to the basement, rec room, etc. or used as a stand for the new TV.
Don't forget people who move into smaller houses or apartments and must downsize. These folks may have had large 23-25" color console entertainment centers that still worked perfectly well, but since the owner was moving into a smaller home with much less room, the set had to go; many of these sets may have been given to relatives or friends, but a lot of these consoles wound up on the curb to die a certain death in a landfill.
Consider as well (as one VK member in Texas recently mentioned in this forum) that many houses in the southwestern, midwestern and Great Lakes regions of the US are built without basements, so there is very little if any room for anything other than furniture. I had a friend in my old neighborhood who lived, with his family, one street over from us in a house built on a slab, no basement. I can only imagine how crowded it must have been in that house (I never saw much of the inside). They had just one TV that I can recall, a 21" Zenith b&w console in the living room. I also remember them having a pinball machine (the old mechanical type, the forerunner of today's digital video arcade units), but I don't remember anymore where they put it.