Cables are critical. Want to stop or shift gears? Cables, sliding smoothly through housing, do that. Cables can last a long time with a little care. Sadly, at re-Cycles we see a lot of bikes with frayed or corroded cables.
A frayed cable end is a safety hazard and may leave you no way to adjust your brakes or shifting.
A simple end cap will keep it all together. The folks at Park Tool have a video that shows how.