There are several reasons, besides the Vegas shooting, that Disney feels the need for these checks. There have been many cases of children being kidnapped and kept in rooms at Disney, human traffickers have used Disney rooms. Then, there is the issue of someone becoming ill in a room, or worse. That's happened many times as well.
So, all of you that feel the need to use door stops or such to prevent someone from entering your room, you had best hope you never have an emergency and call for help. Drastic? Sure. I've been at WDW about three times since they started this policy. I've been at OKW, Polynesian, All Star Movies and Music. Only one time did I have someone come to my room while I was there. It was midday at OKW, I hadn't hung the 'room occupied' sign out They knocked gently, I answered the door, the CM said he would be just a minute, he emptied two trash cans and was gone within 2 mins. I never saw anyone at the Polynesian or Music. At Movies, I did forgo housekeeping. I had a visit, on my first day, from a CM that wasn't a housekeeper. He asked if everything was okay, I said it was, and off he went. Never had trash emptied, but someone may have entered my room. No idea if they did or didn't.
It's just not a big deal for me.