I'm still looking for the value proposition of the "HUB". What function does the Hub provide that one cannot do by just adding trip days before/after any day in the Itinerary?
I like to use trip planner hubs to organize my trips by sections. For example: Home to Main, Acadia Area, Hampton Area, etc. How hard would it be to allow users to select any number of continuous day trips and add a hub header to the selected days? It improves organization for me and lets me add days while in the area.
As Pseabolt says, the main advantage is organization of your trip. If I'm going to multiple cities, it's nice to have the time in the city separate from other cities and the time spent getting to the city. There are some functional differences as well. For instance, if you choose lodging on a day in a hub, BaseCamp can propagate that lodging to the rest of the days in that hub. If you aren't planning on spending more than one night anywhere, then the value of hubs is minimal, but if you are planning multiple days in a place I find it handy.