In the days of downtube friction shifters and their relatives, the stem shifter, the barcon and the original mountain bike top-mount shifters, the shifter itself changed position for every gear. Thus it became the gear indicator.
Like another lost art, semaphore, the progressive shifter sent its message by gesture. It could be read by those who knew the code. Because the message was extremely simple, even an inexperienced reader could get the general idea that a certain position indicated harder or easier gears.
Late models of mountain bike shifter had little hash marks on the top to indicate with more precision where the indexed shifter had placed the gear. Downtube, stem and barcon models don't offer themselves to the eye as readily, so visual indicators do no good there. In those cases, a rider would become familiar with the angle of the lever in hand to get an idea of the gear selected.
With shifters that return to original position between shifts, gear indicators appeared. Some of them worked. But confusion reigns among the inexperienced. The technician has to explain to the new bike purchaser how four levers now do the work once done by two. If the system has no indicator, the novice rider goes off for that first critical test ride trying to remember which lever does what when why and how. Bikes often return to me in small-small or big-big cog and chainring combinations.
More than one customer has brought a new bike back because "it ran out of gears." The rider had shifted all the way to the end of one lever's range and didn't remember that there was another lever there to bring the chain back.
The rider isn't the problem. The plethora of unnecessary complications is the problem.
An industrial corporation wants to be able to tool up for large production runs. So Shimano and the companies forced to chase after Shimano's marketing machine promote the use of shifting systems grossly more sophisticated than many riders need. Marketing tries to convince them they want it, but OEM spec simply crams it down their throats. Then the backlash hits and we get things like Auto Bike, Land Rider and Lime. Dumb it all the way down.
The industry has not taken all alternatives away. Down tube and barcon shifters are still available after market. But putting them on a bike represents extra trouble and expense. And top-mount shifters for a flat bar are either cheap friction models or the expensive (though clever) Paul Thumbies.
Manufacturers of complete products (like complete bikes) want to sell complete products. They don't see any advantage for themselves in offering something versatile, durable and repairable if they can convince enough consumers to drain the warehouses of another whole model-year's worth of new bike inventory. But that can't continue to work (if it ever did). It isn't sustainable without a return leg carrying the carcasses of the discarded bikes back into the cycle in some form.
As bicycling recognizes its many niches and each sub-category grows as the population grows, masses of mass production will fail to serve the needs of the biking public and the industry itself. The giant corporate approach will have to break up into either smaller divisions within the overall corporation or smaller, more nimble companies devoted to their niches. To some extent, that is happening, but component spec lags behind. That's why the most creative growth seems to be occurring in single speeds, fixed gears and BMX. These are the least dependent on integrated technologies, and therefore offer the companies and their customers the greatest opportunity for individual creative expression.
Component companies need to think beyond the brifter. They need to quit dictating which category of rider gets to use what width chain and range of gearing. A large portion of bicycling doesn't fall into a category. The bike is a starting point. The harder and more expensive the industry makes it to get from that point to other points, the more they make bicycling seem like a big yank and just another excuse for companies to suck money out of consumers' pockets.