Check into a hotel room in Idaho and this won't happen. Check in to one of the hotels in the city who makes its money on tourism where the worst shooting in the US occurred and here we are. We are talking about 5 Miles of Las Vegas Blvd.
The fact that it can happen at all, anywhere, even on just 5 miles of Las Vegas Blvd, is a stark reminder that the US has very little in the way of legally-mandated privacy protections.
Mass shootings happen because the US has one of the most-armed citizenry in the developed world, and because we have ridiculously backward views about how easy it should be to put deadly weapons in the hands of anyone who wants one.
Daily room inspections are not going to stop any mass shooting where the shooter is aware of the inspections. The 2017 case was egregiously bad, certainly, with the shooter able to bring an insane amount of weaponry up to his room. But he could have been just as deadly with the contents of two or three regular-looking suitcases, something that wouldn't have raised any red flags during daily room inspections.
There hasn’t been another mass shooting on the strip in the following 7 years and this policy makes the scale much harder to replicate. I don’t know if this policy is responsible or what else is being done but to dismiss it as security theater seems too easy. If it is a deterrent, it is working and if it limits the scale of a future attack as mentioned I understand the policy.