I've heard mention that the power requiremments for Bluetooth make a Bluetooth-enabled meter impractical.
Another issue with Bluetooth is legal: keeping medical data private and secure over radio channels.
A number of meters do use USB cables; others use serial-to-USB connectors along with serial cables. Sometimes you need to search third-parties and/or further afield to find the appropriate USB cable.
I did some meter reviews earlier this year, and have USB cables for the following meters:
Note that each meter company has a proprietary interface or set of data transmitted across the connection, so the Advocate cable and software doesn't work with the Freestyle monitors, or vice-versa. The meter companies tell me the proprietary set-ups are required to maintain privacy of medical information.