Example: a HW company spends millions, if not hundreds of millions, on developing a new chip/board, expecting the investment to be returned on sales. China steals the IP, and starts manufacturing and selling before them. Company loses all investment on R&D.
Example: pharma company spends hundreds of millions developing a new drug, including decade-long, gruesome FDA approval, expecting to return the investment on sales, including China. Someone steals the documents on manufacturing it. China starts producing the generic before the company even obtains permission. China patents the generic there, so chances for sales in a 1.2 billion economy are zero. India probably follows. Why bother then?