Manufacturers generally sell one vehicle that covers various markets, with different tax and emissions regulations; different climates with extremes of heat, cold, humidity, different fuel qualities, different operating altitudes, etc.
A manufacturer has to take all of these factors into consideration and make substantial compromises in the vehicles operation.
Sales and marketing also have a big affect on the way an engine is mapped. Low spec models often have the exact same engine hardware as the high spec models, there often can be 50 BHP difference between them yet the only difference is software.
If you look the in manufacturer brochure at the engine specs, the torque graph will rise, then flatten out on a straight line, and then drop off. This obviously isn’t how an engine breathes, and it’s the request of sales and marketing to produce this flat lining of the torque. Why? Well it’s about having better torque figures than the competition and about local market taxation laws.