Las Vegas arterials generally lack parallel parking, and that's generally desirable for bicycling. For pedestrians, it is undesirable to have motor traffic traveling adjacent to the sidewalk.
Las Vegas provides an interesting lesson in the relationship between the private and public realm. As this photo demonstrates, private property along Las Vegas streets begins immediately behind the sidewalk, so there is no way to move street furniture back, or to install a grass strip between sidewalk and street, or widen the sidewalk without narrowing the street. So, these boxes displaying promo material for some of Las Vegas's more colorful entertainment options cut into the width of the sidewalk.