Don't blame Shimano, blame the American bicycle distributors and, by extension, the American consumer. During the early 1970s bicycle boom the average American consumer couldn't tell the difference between a Peugeot U0-8 and PX10. For that matter, most still can't. They were confused by the fact that several models within a line could carry the same component (or what appeared to be the same component) and that there was such a myriad of component manfacturers represented on one bicycle. The distributors wanted a better method to differentitate between models and therefore make it easier to sell the product.

Shimano reacted to situation, unlike a lot of manufacturers. Thus began the proliferation of rear derailleur models and the development of groups. Of course, to make it easy to tell the difference, you had to have a big model name emblazoned on it. Basically, it got to the point where you had a group for almost every single model (i.e. price point) in a model range, so the consumer could tell difference. If the consumer could tell the difference, they could justify the price differential and just may step up to the higher priced (i.e larger profit margin ) model.

Of course, you also have to make things noticeable when things changed, so the consumer knows that there is a newer, better version. Consequently, each successive generation got a new name. 600 begat 600EX, which begat 600AX. which begat New 600EX, which begat 600 Ultegra, which begat Ultegra and so on.

Shimano's reaction to the consumers' confusion is part of the reason that they became the dominant component manufacturer. Give the consumer what they superficially want and they will buy. Most European companies reacted to late, if they reacted at all. Even into the 1980s, it was hard to tell one Simplex derailleur from another, at least for the average consumer. You still got Simplex derailleurs paired with Mafac brakes and Stronglight cranksets. It was too confusing and when a consumer is confused, he typically gravitates to and buys the simpler solution. Consequently, Shimano prospered and most of the Europeans faded away, with the notable exception of Camapgnolo. They survived on past reputation, but didn't really learn from the experience. They expanded the groups but it was still hard to tell them apart.

The American consumer likes to buy entities. Whether they're buying a car or blender, they don't want to have to been concerned about the quality of each individual componet to make sure they're getting good value. From this aspect bicycles are unique. All the individual parts are on display, subject to scrutiny and concern about their performance. Shimano's strategy of a different gorup at every price point allayed a lot of that concern, as everything matched and the consumer could tell that bicycle A was different from bicycle B, justifying the price difference. The approach simplified things and made the bicycle more of a entity than a mish-mash of apparently unrelated parts. Of course, the system approach also results in improved performance, as all the componets mesh for optimum performance. However, this was secondary to making the purchase decison and sale easier.

It may be hard to remember all the names and their hierarchy but it certainly is easier than picking up a 1990's Campagnolo equipped bicycle where you can't even identify the components or an earlier European model which appears to be a frankenbike. With Shimano you generally have a solid footing and the answer to the level and era can be found with only a few clicks of the mouse.