The bike industry is full of better mousetraps that are mostly better for the mice. I guess that's true of all areas of technology. Can't blame people for trying, although sometimes I get really pissed off that they persist on some lines to the detriment of others.
Today I was examining a road bike with yet another case of STI shifting that would not index accurately. This was isolated to two gears at the top of the cluster, not quite the lowest, but in the neighborhood. The mis-shift was so consistent and crisp I thought it might actually be an internal ratchet problem rather than congealed shifter lubricant or a cable or housing problem. But when I checked the cable as a matter of course I found a frayed, splayed Cable of Death getting ready to pierce the brifter's brain. I was able to extract the cable and its shards by a judicious use of sharp probing implements and a magnet. Good thing stainless cables are an alloy that responds to a magnet.
So: if your bike has weird shifting issues or won't stay in one or more gears, go straight to the cable first. Especially with road brifters, the shifter you save may be your own. And the money.