WHY...are there so FEW tv's..from the late '60's -to mid-80's STILL AROUND?

[Electronic M]

Part of it is cabinet quality. Newer sets tended to be particle board, fake wood, plastic or metal, and did not have the 'it is still a fine piece of furniture' excuse to keep it when the repair man eventually advised a newer set would be cheaper than a repair.

Part of it is weight (the newer ones tended to be lighter and easier to bring to the curb).

Many of the newer sets were cheaper and less reliable so the owners felt less committed and saw them as junk faster. Also tech changed a lot then, and sets got really cheap (and repair started drying up) by the time many were acting up.

A good portion of cabinet styles then were less timeless than earlier models and would wear out their welcome after redecorating.