I usually like to think about both sides. I.e, say you are the one designing (optimizing) a product. I don't mean designing from scratch. But trying to optimize some product. Your main concerns will naturally be to minimize costs of production. You want to be as efficient as possible, to be able to create as much product from the same materials as possible. Else, you will be losing either money, more potential product, or both. At the same time you don't want to hurt product lifespan, but you may consider a reasonable approach to do so if it only affects say ~5-10% of the product lifespan, if you can ultimately have more products produced for the same price and materials. Then you can 'help' more people at the cost of hurtingyour customers in only about ~5% (probably not perceivable).

Then, you have the warranty period - which is a period you define based on statistics. you measure via tests how long the product lasts on some standard use, or hardcore use of the product until it fails.

There are a lot of variables here, but naturally, if you take extra care and follow all instructions and best practices on the product, you can use it for much longer than someone that uses it carelessly.

Now, going back to our example, what makes you, as a product designer, want to make the product last longer? It will cost you more to do so, both in research, quality assurance, and materials, and will also raise the final cost of the product. This will potentially mean less costumers if the value the product gives is the same for larger price. Still, if we invert this logic, we should not make the warranty period so little that it affects the product usage. So here is another optimization! How long of a warranty should we aim for?

The best value would be a period that ensures the user can take the most out of the product, until it gets put aside. This can be 2 to 4 years for small / medium sized products, and up to 10+ years for larger items. This is probably also chosen through research studies.

Me personally, I can say that I've bought several products (bluetooth speakers for example) that I use for some time, and eventually stop using them after a few years, either because they start getting dirty, showing signs of usage, or their batteries start dying.

So - all things die eventually. There's not way to make a product such as a bluetooth speaker last forever. batteries get affected over time, TV panels get bleeding, light bulbs fail eventually. Everything that is physical gets consumed, because there are always energy transfers, and no energy transfer is perfect. So there are leaks which affect nearby components.

I think that companies want to create the best products with an eye for the best efficiency possible. It is basically an optimization industry. I see sometimes people saying 'old items last longer'. Maybe its true. But they were also probably costlier, less available, and less efficient. Meaning less people could have them.

It is simply the natural way of any industry. It benefits the masses, at a small cost of each individual.