The Mountain wasn’t the most swoonworthy knight back before he was poisoned by Oberyn Martell; the zombie version of The Mountain (going by Robert Strong) isn’t going to sweep any starry-eyed lovers off their feet any time soon.
I’m not surprised to see that he doesn’t have anybody by his side, though.
Sometimes, even a bloodthirsty murderer is in the mood to take off his shirt, make himself comfortable by the fireplace, and read some poetry while smelling the sweet scent of roses.