Easy. Low-cost imported goods, shoddy construction, and “solid state” electronics.
For example, in an old TV, one could pull an assortment of vacuum tubes out, test them, and replace the faulty one. In a modern TV, if some random component dies on the “motherboard”, it’d take an expert many hours to find the damaged part, and it would then have to be unsoldered, and the replacement resoldered in it’s place.
Highly skilled labor charge, five hours plus parts, $285. Cost of replacement TV, $250.
In modern VCRs, the gears and drive linkages are all plastic. If a gear strips or some bracket breaks, replacement parts simply are not available. The factory simply doesn’t sell individual parts. (Besides, would you like to explain to some factory guy in China or Taiwan that you need that little black lever at the back of the cassette-lifting mechanism that trips the capstan preload arm?)
In that case, it can’t BE repaired, unless the repair shop happens to have a duplicate on the scrap pile that doesn’t ALSO have a stripped gear.
In the case of some things, the damage occurs to the main casing, typically plastic. For example, I once tried to fix an old Black & Decker drill. The brushes had worn, and I thought it was an easy fix. Except the worn brushes had heated up and gotten crosswise, and both melted and cracked the body halves. Since B&D doesn’t sell the body sections- and if they did, they’d be 3/4 of the cost of a new drill- it was essentially unrepairable.
Furniture… heck, there’s a subject long enough for a book. The steel framework that holds and operates things like the footrest and recliner mechanism, typically uses a simple stepped rivet, rather than a hinge. That rivet eventually comes loose and it breaks or binds. The wooden framework for the rest of the chair or couch is so thin and of such poor wood that if you went in to try and fix it, there’s no wood left to drive another screw into- it’s all splintered and cracked.
Now, in all of these cases, a sufficiently talented individual with the right tools and knowhow, can fix many of these things. But he or she is not typically charging oneself… Were you to have a professional do it, again, chances are the cost of the fix exceeds the value of the object in question.
Personally, I’ve fixed a great many things. Including one or two things that weren’t designed to be taken apart (riveted or welded shut, for example.) But I’ve also occasionally chunked the old part and simply spent the cash to replace it too.
On a whole, I also firmly believe that there are fewer do-it-yourselfers, comparatively speaking, than there were years ago. An example of this is that recent news piece in which one of the top TV news personalities- who’s been on the air for decades- stated he has no idea how the TV picture gets from the studio to the individual TV set.