Manufacturers want to keep it simple. The more options they attempt to offer, the more it costs complicated it gets (planning manufacturing, distribution, marketing etc.). COmplexity costs money. Make it simple. Start from a base model and add trim levels that add a bunch of features based on what customers normally pay. The person willing to pay for the big engine is more likely to want the leather interior or the sunroof or the bigger tires etc. It generally makes sense and anything that helps save money helps the seller & the buyer, but is of little comfort to anyone with specific tastes/needs.