At the same altitude as the starting point, a destination with a mountain in between requires a climb and a descent. A significant milestone, apart from the final destination, will be the highest point of the mountain. You’re halfway there.
After that point, nothing is the same. There is less ground to cover than what has been covered. Logically, that’s how the concept of 50% works.
Being able to express 50% progress implies understanding the whole trajectory. Without, there is no telling if the goal is approaching and if the effort to get there will require more, equal, or less energy than up until the point where you are now.
Quantifiable goals, expressable in a combination of numbers and time, are crucial for a business and its people to motivate themselves and others around them.