Not everyone can transport a bike inside a car though. Also, I personally don't like having to put the wheels off/on as part of the process of getting a bike into a trunk. Trunk racks are sort of a compromise, relatively inexpensive (and the ones today are nicer than ones from 30 years ago) and they work ok, but I don't like the fact they inhibit getting into the trunk. They are ok for transporting one bike, but two bikes are sometimes hard to attach without having them bump together and I also don't like the additional strain on nylon straps two bikes entail. Probably ok, but two bikes would make me nervous over rougher terrain.
Got a Kuat hitch rack a few years ago and never looked back. Easier to attach than a trunk rack and esp. a roof rack, no wind drag, no wheel removal, and it seems highly secure. Only disadvantage to it is that I have to remove a front fender to use if the bike has that attached.