If you allow people to not be present at all, then some will turn this into a business and operate a real hotel room, 365 days a year. Operated like a cheap hotel. I can see why the government may want to regulate that.
An easy way to distinguish the above situation from legitimate friends staying over, is to ask for the owner to be present. Or couchsurfing. That tends to make it a more casual and better controlled environment. I can understand why the government may want to stay out of this.
My impression is that the real criteria should be how much the room is rented: if you have guests 300 days a year, you should be regulated. If it's 10 days, leave me alone. The problem is that it's probably hard to define, and may impose its own set of requirements (such as, everyone would have to keep a registry of all visitors, just to prove that they don't fall into the hotel category).
I thought it would be instructive for people who talk about "government" as if just putting the word big in front of it solves the issue, and the solution is cut taxes for rich people. None of that has anything to do with this. This is a concrete policy change in a specific area.