Advancements in technology, especially those advancements in recent years, have made it possible to provide most cars with exceptional performance. We know that performance is a selling point for many consumers, so this is something the auto industry pays attention to and incorporates as one of its metrics.
Many of the technology developments of the past years have been able to either decrease fuel consumption or add performance to the engine. So, in countries where there is a high disposable income and relatively low fuel prices, performance is chosen over reducing fuel consumption.
Technologies such as 4-valve engines are an example of how certain technologies, when utilized, can lead to increased performance and/or provide better fuel consumption.
There are many other technologies where the same choice can be made. With the advent of new CAFE standards in the U.S., manufacturers will have to choose to reduce fuel consumption where possible over increasing performance. In the EU, due to the high fuel prices, this choice has already been made in most cases.