The advantage only exists today. Personally, I have a short range EV that gets used for all our city driving and sometimes we go on longer runs when speed isn't important but I also have a petrol car for my regular long trips. If I didn't have to do those trips weekly, I would just hire a petrol car as needed. The added complexity of having a petrol engine undoes much of the simplicity of an EV which is why I didn't go for something like a Volt. A PHEV is a short term solution IMHO and in a few years they'll be obsolete, especially the ones that have very low range like the plugin Prius.