It's another number to stare at. If I'm just ticking over then I'll pick random numbers to hit. Like "keep going until 1000 calories, oh you're on 39k, keep going until 40k"
But yeah, I don't actually "use" either value. Neither do I use it on the road though to be fair.
Except everything heats up. And you have gears. And now you have power.. (!)
Never will understand why people think turbo speee/distance is a thing.