Actually, its cables do to ensure the best shifting and braking
Your bike needs to stretch before a ride, too
What key components do most bicycles have in common that are also some of the cheapest to replace? Cables, of course. Remarkably, these steel-braided lengths of wire do a lot of work. Without them, you woudln’t be able to shift gears or slow down.
One thing that can affect the performance of those inexpensive and essential components is cable stretch. What is that? A cable elongates slightly with use. Shifting to larger cogs and rings and braking applies tension to the cables. Over time, performance suffers as the cables get longer. Also, the housing settles into the ferrules, while the ferrule ends settle into frame stops, shift lever bodies, and barrel and inline adjusters. The housing itself will also compress slightly. All of the above will contribute to decreased braking and shifting performance.
Have you ever bought a new bike only to have it jump gears after the first ride? The cause is almost always the stretching and settling I mentioned. The shop didn’t properly “pre-stretch” the cabling systems. Most of the time, when a new bike is built at a factory, it is slapped together without care taken to ensure lasting shift and brake performance. When I build a new bike or replace any cable, I will always pre-stretch, re-adjust, and then do a final test ride.
top left Stretching cables on an externally cabled bike
Stretching cables on an internally cabled bike
Campagnolo shifter cable end on left, Shimano on right