Hi Don,
Manufacturers compete with one another at various price points. The base coach may be priced "starting at" $50,000 to compete with a similar competitive model priced "starting at" $50,000. Both manufacturers then add forced options at additional price to create the set of features that will sell best. As a marketing device, they can advertise and draw you in to look at a "starting at" $50,000 coach. By the time you're done, it may price out at $70,000. They don't make these regular options because they know that most people would be unhappy with the result.
You probably have seen car commercials where the big font says "starting at $18,900" but the fine print admits that the car as shown in the commercial actually costs $27,550. While the car commercial may or may not involve force options, the concept is similar.
Also, sometimes manufacturers will enter into special order agreements where company X purchases the base model from company Y and then re-brands it as a company X product with a somewhat different set of features. Making forced options instead of calling it a standard feature set allows for special contracts.