I've said "to prevent and offset". It's about managing the event (offsetting the bad cases when prevention fails). Having a reception area allows you to have their signature on the contract, to validate their identity (name, nationality, passport) based on the photo ID and how they look in real life and to have on record a lot of validated information about them (which will sure help with police and insurance in case something bad happens).
I agree identity validation, and being there to hear loud noises/odd behavior makes it harder / less fun for an attacker -- but this is not what allows hotels to operate effectively. Some percentage of hotel registrations surely occur with stolen passports, etc. Hotels rather build this cost into their business model in a manner similar to an insurance company.
Because hotels rent so many rooms at a time, they can treat these costs in the same way that your car insurance company treats accident risk -- something that is always happening that can be offset in real time by honest people using the hotel as per the contract.
Letting people into your home does not have that risk-sharing property -- it's insuring a single driver instead of tens of thousands -- you open yourself up to a very real risk of losing a lot of money.
(Not to mention that hotels are not personally attached to the rental rooms).
