Why are units of measure important when solving real-word problems?

In physics, we always measure quantities and compare them with a standard. That standard defines a unit of the quantity. Suppose you want to measure the length of a car, so you use a meter stick, which is the standard for measuring distances. Then, why are units of measure important when solving real-world problems? Well, because when solving problems that involve equations, they need to be dimensionally consistent, but what does it mean? it means that you can't add two terms having different units. For instance, you can't add apples with tables!