I use combine to subtract multiple masks for Unreal Engine layers to get more precise layers. As you can imagine, this really starts to bloat a graph.
In Houdini, there's a node called Heightfield Combine Masks - In the attached image you can see how each mask input then has a blending style, and it just works like if you stack combine nodes. I've found that incredibly helpful just keeping your graph clean and organized.
The ability to combine any number of inputs in a single node would, in my opinion, be a really welcome feature.