Actually, the idea is to reduce the cost, increase the profit, and reduce the lifespan so the suckers have the buy again soon. But I digress. I am way too cynical for my 26 years.
Despite your engineer status, you are clearly no engineer. George Harris is and I was until I retired. There are an enormous number of trade-offs made during design, and nearly all affect each other in some way. The design space is so large there frequently is no definitive way to find the optimal solution. Many times design requirement changes will impact the finished product in very unexpected ways. And yes, without profit, there will be no product.
Reducing the design life of a product is sometimes a desirable thing, how many people would still use the Motorola "brick" if it was still viable? Any remaning life was wasted cost in design and build.