There's also the fact that they're one of the most common obstacles people face in their own driveways. On HW 2.5 we've had ours read as a pedestrian before, which can be confusing/alarming. (I know that HW 2.5 doesn't/won't get the new visualizations, but it does demonstrate a use case.)
Perhaps at some point Tesla should implement a generic "obstacle" object in the visualization. There's a lot of stuff that
can show up in a roadway, but doesn't show up very often. Will there be separate visualizations for, say,
sofas? I doubt it. Cones have a special meaning in the driving environment. Cars, trucks, motorcycles, and pedestrians can all be expected to exhibit certain ranges of motion. At some point animals should be added as well, for the same reason. But big lumps of stationary stuff are pretty much just big lumps of stuff, no matter what their original purpose--an FSD car should just stop and/or drive around them if there's room. So those kinds of things won't need to be visually differentiated from each other on the display.