Jaime "Case" Griesemer, longtime Bungie designer, gave a talk at GDC about game balance in Halo, with some specific mention of the sniper rifle:

Spectacle, too, is important to keeping players in flow, with the sniper rifle creating a contrail and sound effects being subject to a delay over long distances. Such exaggerated causality makes the gun look good on YouTube, because viewers can easily see what's happened, and players don't break out of the game's flow in order to figure how what's just happened. And most sniper rifles aren’t fun, he claimed, because they don’t generate flow.

A full rundown of the talk is over at Edge Online.