I have not heard a reason. Guessed it was because of the million dollar houses across the highway. In May I was at my Grandson's baseball game at least 10 miles away on a Sat AM and i could hear the guys cleaning there tires before a run.
Group photo taken for the 1978 TV special “When the West Was Fun”. (L-R front row): Dewey Martin, Johnny Crawford, Chuck Connors, host Glenn Ford, Alan Hale Jr., Henry Darrow, Larry Storch, Neville Brand. (L-R second row): Denver Plye, Iron Eyes Cody, Harry Lauter, Jeanette Nolan, Linda Cristal, John Ireland, Darby Hinton, Joe Bowman, Fred Putnam. (L-R third row): Pat Buttram, Milburn Stone, Dan Haggerty, Guy Madison, Rex Allen, John Bromfield, Keenan Wynn, Jackie Coogan, George Montgomery. (L-R fourth row): X Brands, Bill Williams, Michael Ansara, Slim Pickens, Dick Jones, Don Diamond, Ken Curtis, John Russell, Peter Brown, James Drury. (L-R fifth row): Rod Cameron, Jock Mahoney, Jack Kelly, Tony Young, John McIntire, Ty Hardin, Mark Slade, Lee Van Cleef, Will Hutchins, Terry Wilson, Clayton Moore, Doug McClure.
It doesn't seem that long ago when Nevada highways had no speed limit. The sign simply read "resume safe speed".