Is there a backstory? Is Riker tall or the chairs overly short? Did they want to avoid chairs moving on screen, or avoid showing his back side? Where the chairs too heavy to move, or are bolted to the floor? Was this to convey he needed more breathable briefs and needed to separate the "boys"? That command was a heavy load? Did this convey a whimsey with his character? Or did he want to accentuate his crotch?