Because "ordinary" people are allowed to pursue their dreams to get rich. For some perspective when you read the news (WSJ):
An American earns, on average, $130 a day, which puts the U.S. in the highest rank of the league table. China sits at $20 a day (in real, purchasing-power adjusted income) and India at $10, even after their emergence in recent decades from a crippling socialism of $1 a day. After a few more generations of economic betterment, tested in trade, they will be rich, too.Read the whole thing.
Actually, the “we” of comparative enrichment includes most countries nowadays, with sad exceptions. Two centuries ago, the average world income per human (in present-day prices) was about $3 a day. It had been so since we lived in caves. Now it is $33 a day—which is Brazil’s current level and the level of the U.S. in 1940. Over the past 200 years, the average real income per person—including even such present-day tragedies as Chad and North Korea—has grown by a factor of 10. It is stunning. In countries that adopted trade and economic betterment wholeheartedly, like Japan, Sweden and the U.S., it is more like a factor of 30—even more stunning. And these figures don’t take into account the radical improvement since 1800 in commonly available goods and services.
[...]Once we had the ideas for railroads or air conditioning or the modern research university, getting the wherewithal to do them was comparatively simple, because they were so obviously profitable.
If capital accumulation or the rule of law had been sufficient, the Great Enrichment would have happened in Mesopotamia in 2000 B.C., or Rome in A.D. 100 or Baghdad in 800. Until 1500, and in many ways until 1700, China was the most technologically advanced country. Hundreds of years before the West, the Chinese invented locks on canals to float up and down hills, and the canals themselves were much longer than any in Europe. China’s free-trade area and its rule of law were vastly more extensive than in Europe’s quarrelsome fragments, divided by tariffs and tyrannies. Yet it was not in China but in northwestern Europe that the Industrial Revolution and then the more consequential Great Enrichment first happened.