Some people just do not know how to have fun. They think everything has to be useful. Luckily, the sine, cosine, and tangent functions do have a lot of real-world uses.
Surveyors use the tangent function a lot.
For example, they can use trigonometry to figure out the distance across rivers. That's the red horizontal line in the drawing. Now we take a sighting on the tree from downstream. That's the black line in the drawing. The surveying instruments will tell us what our sighting angle is.