I find SNAs useful for one night stays at less desirable places when I use my Chase free night award.

Example would be Westin South Coast Plaza in Costa Mesa or Westin Bonaventure in DTLA. If I have a show downtown (which can be 2 hours in traffic for me), and a spare Chase cert, then I'll do dinner and a show and stay overnight. Maybe I'd get the upgrade without it, maybe not.

For the places I truly want to go to on vacation, where I'm staying for 5 nights, they almost never clear.