Why arent ice caps or mountains considered biomes?

Ice caps and mountains are not considered biomes because they are part of the biomes. For example the mountains are high up so they are cold which means that it's biome would be grassland or tundra, depending on where it is located. Ice caps are located in other physical features like mountains, oceans, glaciers, etc. so its biome would be tundra. So basically overall biomes just describe the climate or environment of a place and mountains and ice caps are actual places therefore they cannot be biomes.