The Grand Canyon is not close to Las Vegas. The nearest edge — the West Rim — is a 2 to 2.5 hour drive each way, and the more famous South Rim is closer to 4.5 hours. A helicopter collapses that into minutes and, more importantly, gives you a perspective you simply cannot get from the rim of the canyon looking in.
There are three broad reasons people choose to fly: time (a helicopter tour turns a full-day expedition into a half-day outing, leaving your evening free), the view (flying into and below the rim is a fundamentally different experience from standing at a viewpoint), and the occasion (canyon-floor landings, Champagne toasts, and sunset flights are a favourite for proposals, anniversaries, and milestone celebrations).
Two more choices shape the experience. West Rim tours can land on the canyon floor — below-rim landings are only permitted on Hualapai tribal land, not inside the National Park. And the aircraft matters: an EcoStar's panoramic windows beat the older AStar when the views are the whole point. If this is your one Grand Canyon day from Las Vegas, the canyon-floor landing is the part you'll remember longest.