Originally Posted by T-Mar

You need to look at this from the context of the early 1970s. Millions of cyclists who had never used caliper brakes, were buying lightweight bicycles with caliper brakes. They hadn't learned that the front and rear brakes require different modulation for the most effective braking. A rear brake with less mechanical advantage and more flex is easier for a novice to modulate, as it's less sensitive. Basically, it made for an easier (and arguably safer) learning curve for the novice lightweight rider. If you've been raised on caliper brakes, even if they were unequal reach, it's relatively easier to adapt to a different mechanical advantage..

If you look back at boom era 10 speeds, you'll see the unequal reach concept employed most widely on the entry level models from bigger brands specifically targeting the USA market. When you stepped up to the high end models, you saw it less frequently because the company often assumed the rider buying a bicycle at this level already had experience with lightweight bicycles and caliper brakes. Also, if it was some smaller European brand, you'd be more likely to find equal reach brakes. After the boom, once the consumer became familiar with caliper brakes, manufacturers started to move away from unequal reach brakes. These are only generalizations and it easy to find exceptions.

Regarding the cost savings, almost invariably, all the parts are identical with the exception of the calipers arms. Shimano continued to offer two reach options of 600 Ultegra into the very early 1990s. 105 had two reach options as late as 1998. If the component manufacturer offers two reach options there's no typically no savings for a bicycle company to specify equal reach versus unequal reach. Any savings would come from simplified logistics in the bicycle factory. In that case it's not saving money but preventing cost associated with mistakes.