I haven't read anything that says WN is rushing to add service at LAS. They certainly aren't going to take over the red-eye bank. WN is smart about such things - they aren't going add capacity just for the sake of adding capacity.

Right now WN is more than happy to concentrate on building up DEN and they added SFO service - they're waiting for UA's demise so they can become the dominant carrier at those airports.

WN has a discipline in what they do that most other airlines lack. It's why they didn't rush in and add 100 flights to PIT, despite the predictions of online armchair critics. It's why they won't rush in to add tons of flights to LAS. IF there's a need they'll add them.

And that's the difference - legacies will add the routes hoping to build the need; WN waits until there's a perceived need and then adds the routes chasing off any weak competitors.