If you can sell stock, or leverage it for loans, then you get access to future profits as soon as there is a reasonable expectation they will eventually show up.

Amazon's growth model was based entirely on this effect for many years. No need for profits, company's value skyrocketed as anticipation compounded.

Of course, there's a whole bunch of other differences, like the machines don't need to wait 18 years after construction for physical labour, they don't need to be trained for 21 years for mental labour, they don't sleep, and the "working lifespan" target is about 47 years rather than the full 84 years average human life expectancy at birth in developed nations.

Because they're not built to, presumably because manufacturers are greedy and want to sell you a new one, and buying a new one is encouraged by consumerist culture.

Let's say effective human lifespan for physical labor is ~40 years (20 to 60). On average, commercial aircraft last 20-30 years, meanwhile the US military plans to keep B-52s in service at least through 2050s, which will make them roughly 100 on average.

It's not that machines can't last a century with proper care and maintenance, it's that they're not designed to.