The ratio of point:dollars costs of different hotels vary widely. If you just pick one hotel "at random", you're likely to see a poor redemption rate.

And if you compare a poor redemption rate (either on hotels or airlines) to cashback, then indeed cashback may be simpler and equally good for those cases.

I don't know where the good redemptions in SPG are, since I don't participate in that program. I do know in Priority Club they are only here and there, like the Candlewood Suites in Jersey City NJ which is often $180 but only 15k points, and one $1.50ish PATH train stop from lower Manhattan, but of course that only helps if you're going to NYC. (The other good Priority Club redemption is if you can find a 5k/night Points Break somewhere you can use, which is hit or miss.) I do know in CHoice they are, for example, $300++ hotels in Norway, but of course that only helps if you're going to Nrway. I know in HHonors a couple years ago they used to be any Scandic hotel for 10k/night, but of course that only helped generally if you were going to Scandinavian (or a couple other northern European) countries, and at rate that's long gone now (first the redemption rates when up, then they Scandic left HHonors).

The good redemptions in airlines are mostly in upper-class long interntaional flights. The good domestic eoconomy redemptions in airlines are typically only for "esoteric" destinations (like when I got Los Angeles-Jackson Hole WY for 25k UA miles when the cheapest flight was $600ish). If you only use miles for domestic lfights at 25k that would cost $250ish otherwise, that's also a poor redemption and again you might as well use cashback.