I, too, decided to put one on a duffel bag I checked a couple of years ago, and it WAS NOT on my bag when I claimed it! So, I don't do it any more. It didn't seem worth it to write in about it.
The only thing they're really good for, are to show off how important you (think you) are to the whole plane!
I did post one time in the past, where I was flying in a Y door exit row on a B752 - boarded late due to late connection - was told I'd hafto check a bag due to no overhead space. When I set my bag down on the floor, the DM tag clinked - the FA's eyes literally dropped down toward my bag, and suddenly, there was overhead space available!
So, I guess there's SOME value!
So, if that makes me a DYKWIA type, so be it!
. . . . . Also, one of my PIT GA buds found one that fell off a bag and actually saved it for me!