The answer to why resides in the way wealth is allocated in society. If you look at the graph of the wealth of the 0.1%, the median income and the economical growth, those three numbers were growing at a steady pace up until the 70~80s. Now our economies are growing at a similar rate but median income plateaued/is decreasing while the wealth of people at the top has skyrocketed.
It's not hard to figure out where all that growth went.
We could still afford such a lifestyle. Or we could learn to share more and end poverty and respect the Earth. But instead we're allowing a small village of cunts to each have more money and power than entire countries.