Here's why:
* Heaps are often unorganized: A heap suggests a random collection, making it difficult to assign a specific collective noun that implies structure or order.
* Heaps can be made of various things: You might have a heap of leaves, a heap of clothes, a heap of stones, etc. Each material would require a different collective noun.
Alternatives:
* You can use more descriptive terms like:
* Pile
* Mound
* Stack
* Mass
* If the heap is specifically of a certain type of thing, you can use the appropriate collective noun:
* A drift of snow
* A litter of leaves
* A pile of rocks
Ultimately, the best choice depends on the context and the type of heap you're describing.