If they did this, I think they could still build a monorail station at the northwest corner of the airport, and build a separate peoplemover line to connect McCarran's Terminal 3 and Terminal 1 to the monorail...
You just found yourself on a taxicab industry hit list…
Not the first time for that...
The taxi lobby has a much bigger issue than me and my random musings, in that the ride-share industry has greatly cut into their profit margins.
While any resort city understandably exists to soak out-of-towners, Las Vegas always stood out to me as particularly egregious in that regard. They have a fine-enough rapid bus that goes up and down the Strip, but doesn't actually stop at the airport. Likewise, the bus which originates from the airport takes a meandering path around the resorts.
I know there's more to LV than the Strip, but most cities I have been to, even in middle America, at least have a bus from the airport to the city center or wherever the main business district is. Truthfully, LAS airport is close enough to the resorts that it should easy to walk, but the terminals are on the "wrong" side of the runway, and I think there's little desire to let visitors avoid the rental car/taxi racket.
Not to be all conspiracy-theory peddling, but the taxi industry has enormous clout and is responsible for that. For decades, the industry encouraged illegal "long-hauling" of tourists through the airport tunnel to pad fares to the Strip, and regulators generally looked the other way, or, at worst, busted individual drivers. Any extension of public transit to the airport would likely be met with fierce resistance by the taxi lobby — not just political donations, but picture a cab strike where drivers park their cars on the Strip and walk away.
As long as the locals don't get affected by it, there's no political incentive for leaders to fix the issue.
The taxi lobby is pretty powerful, but I think their influence is slowly waning a little bit. The "long-hauling" issue hasn't gone away, but there is more enforcement of it now. They lost out with the ride-share issue. And I don't think I've heard much about taxi companies opposing the latest monorail extension plan.
As for transit between the Strip and the airport: It actually doesn't make much sense for the Deuce or SDX to jog over to the airport, as they would miss several of the stops along the south Strip. Route 109 actually goes from the airport to the South Strip Transfer Terminal, which is also where Deuce and SDX terminate--so the transfer is fairly easy. But I think you'll find that more tourists would rather take a taxi/Uber/Lyft when lugging their luggage from the airport (curbside arrival to the hotel as opposed to walking up to their hotel from the Strip sidewalk, which can be a walk for some resorts), but then take other options including bus when exploring.
The whole monorail thing has been a boondoggle since it started anyway. The county keeps trying to make a go of it, but between the taxi lobby and the costs, it's not going to go anywhere ever.
The monorail was actually constructed and is operated by a private company. Clark County doesn't have a stake in it.
A recent Las Vegas Review-Journal article indicates the monorail's ridership projections are going to fall short of predictions this year as well. Uber & Lyft are the culprits (the last ridership projection didn't factor ride shares into account).