Because there would be more trade which will benefit the merchant.
China was itself an established empire and could not be conquered the same way as they did Africa and India.
What you are saying is basically equal to saying why not land in England (during that period) and turn everyone into slaves.
Since that is impossible, establishing spheres of influence allows major powers to break China from the inside.
The major powers of europe, Japan, and America ganging up on china during those days is the main reason behind China's firm foreign policy today.
These advances in the history of technology stimulated societies to adopt new ways of living and governance.
Sumerian cuneiform<span>. </span>Sumerian cuneiform<span> is the earliest known </span>writing<span> system. Its origins can be traced back to about 8,000 BC and it developed from the pictographs and other symbols used to represent trade goods and livestock on clay tablets. Originally the </span>Sumerians<span> made small tokens out of clay to represent the items ...</span>