"The strip" isn't one place. It's several miles long. It's not walkable for people with luggage. To do what you propose, you'd have to not just build it to the strip, but along the strip, which is a whole different problem. There's not a lot of space to build a rail line there. It would have to be a block or two away at best. And then, well, the stuff on the other side of the strip is now three blocks away. For people with luggage. In 105 degree heat in August, or in sandstorms, or sometimes in snow.

Las Vegas Boulevard is like 8 lanes wide. Get rid of two car lanes and now you have plenty of room for a rail line.