If you have two groups unfurled in Layers — good luck in positioning an object between them in Layers. Any spot you drop it in will move it into either group, like the first attached GIF shows.

And if the object is originally within a group, you’d have to move it outside first, collapse both groups and only then put it in-between... when you have a complex layer structure it can be very painful.

Unlike in Photoshop (GIF 2), Send Backwards / Send to Back won’t move the object outside of the group, and dragging the layer to the left side of the tree doesn’t work s well — in Photoshop it just works, in Illustrator we get the 'forbidden' cursor.