people quit doing things themselves , or lost the ability , or got lazy...I knew the end was near when they became glorified cell phone stores a decade ago
I would say it is a mixture of many things. Things used to be much easier to work on, at the same time it was cheaper to fix than buy new. Over time things become harder to work on, and also become cheaper in cost meaning that it is cheaper to just replace them. In 1980 a 19 inch tv would cost you about $600. Minimum Wage was $3.10 at that point in time. That is 193.5 hours or 4.8 weeks at 40 hours a week of work to by that TV. If it broke you would be more willing to spend the $50 or so to buy some part to fix it vs another $600 for a new tv. By comparison most people are probably buying tvs for $200 - $300. Minimum wage is $7.25 so now you are at 27.5 - 41.3 hours so less than 1 week at 40 hours a week to buy that TV. By the time that TV starts to have issues, sure you could pay $50 - $100 for a part, or for a little extra you can now buy a much better TV than what you had before. back in the 70s and 80s. There wasn't anything that extreme between one year to the next. We have much more technological advances now every few years that makes keeping your old stuff pointless. Sure you could keep a freezer or fridge for 40+ years, or you buy a new one that will use less power and pay for itself in a few years, while probably doing a much better job of keeping your stuff at the right temp. You could keep your old tube tv alive, or you go buy a cheap 4K tv that will be better and larger. In a way it is the same as cars, with old cars you could just about climb into the engine compartment when working on them. Now you need special equipment and tools to be able to do just about anything. Can't think of which car it was now but to change the battery required removing the front driver side tire, then the entire wheel well to get to the battery housing. So over time the need for people to fix things goes away as the cost to have them fixed by others or to replace them gets cheaper and the ability to fix things on your own gets harder and harder as things get smaller and smaller, along with getting more complex in their nature.
It's not people being lazy or losing the ability. It's just easier to order online the exact thing you need for cheaper than you'd pay at radio shack. Add to it t was hit or miss whether radioshack would have the item/s in stock
it became easier to order online as it is easier for a national or world wide reseller to be able to have everything in stock as somebody somewhere will want it vs a store front that has to make their choices based on what most people will buy. if Radio shack can only sell 30 widgets through the entire USA they have no reason to stock them as they don't know where to have them ready for people to buy. An online store however can hold 30 of the widgets knowing that somebody will buy them and be able to get all 30 customers to their site to sell to them.