Breaking into a hotel room, and breaking into a hotel room without sufficient surveillance resources are two different things... Just off the top of my head, I can think of a few concerns. You'd need a rotating team of at least three persons to verify that the subject has left the hotel room, and isn't going somewhere for a very short time such as to the hotel laundry room, to a lobby snack bar, or such. You don't want to be surprised in the middle of installing a rootkit. Then you have to deal with the fact that the front desk staff might speak to the person later, like "Hey just checking your new key card worked OK?" "What new keycard?", alerting the person that something is fishy. You have to deal with the possibility that the person might have left a portable motion sensitive alarm stuck to the inside of the hotel room door, or a tiny camera somewhere in the room.

Lots of things can go wrong with this sort of plan. But it's not a one-person job.

You might have your rootkit totally prepared and ready to go, and find that the person has a sub-1-kilogram sized netbook/small laptop that they take with them literally everywhere they go, in a backpack, small bag, or purse.

You might have an attack prepared and get there to discover that the laptop has had its USB ports disabled in the BIOS, with a BIOS password set, and insufficient time to work around that.