My Take: Too far to walk to from the strip, in an odd neighborhood (mostly employee parking lots and adminstration buildings). LED TV screens aren't interesting anymore.
As for advertising, you can't see it from the strip unless you're looking for it, and then it's too far away for that "wow" attention grabber.
https://lasvegassun.com/news/2023/nov/08/las-vegas-sphere-reports-984-million-loss-cfo-quit//