I guess that TomTom produces one version of the software to cover many models, some of which have Bluetooth and Traffic built in so those with lesser capabilities end up with menu entries that are not applicable.
I have a 730 and also a one XL. The XL does not have Bluetooth capability but lists the option because its runs the same software as models that do. The main use of bluetooth is to connect to a bluetooth enabled mobile phone so that you can make phone calls and answer calls through the GPS unit handsfree. Much safer. The GPS unit with bluetooth has an inbuilt microphone and speakers or you can connect to the cars FM radio to provide a very neat phone solution. The 730 does this extremely well and was well worth the extra $.