When a compound shape (not a compound path, but a live result of any Pathfinder operation) is used as a clipping mask, Illustrator does not display edges for the resulting objects.

1. View > Hide Bounding Box (for clarity, to see the issue better)
2. Draw anything
3. Create two intersecting rectangles
4. Select these two rectangles, hold Alt and click Unite in Pathfinder panel to get a live compound shape
5. Select both the compound shape and the art below
6. Object > Clipping Mask > Make

The resulting object has no edges drawn and can’t be seen as selected, until you enable the bounding box. There is no reason to not display the edges for it, except for the carelessness Adobe has about maintaining Illustrator a solid enough tool.