Safety might seem like the most obvious reason to avoid anything resembling tailgating, but your vehicle will thank you for increasing your following distance as well. It allows you to make speed adjustments more subtly, reducing the amount of hard braking and acceleration you’ll need to do. This is probably pretty self-evident, but perhaps reading it will help bring it front of mind next time you’re following someone in traffic.
The only downside to allowing extra space behind the car you’re behind is that someone may take advantage of the slot and cut in front of you, ruining your efforts and ambitions of saving fuel and brakes. Alas, this is a reality of road travel you simply can’t avoid but can only hope to minimize by staying as aware as possible of all vehicles in your vicinity.