Libusbtmc is a wrapper that translates the calls to NI-VISA, libusb and the linux kernel driver to one API.
The reason to use this library would be to write multiplatform software for USBTMC devices and this would be the only reason to use the library. In case you're developing for a single platform only, there's no need for this library, but it's likely that future Admesy examples and function libraries will be based on this wrapper to make examples usable on different platforms.
Currently this library is only available for Windows. Updates expected soon.