Software Defined Radio hardware
Data rate => bandwidth.

USB will handle only a limited data rate, and the entire digitised bandwidth would have to fit into this channel.

With an FPGA at the remote end, it can crunch the digitised bandwidth down to the actual channel bandwidth, which could be one or two orders of magnitude smaller, and send that down the USB. It could go further and demodulate the data, for another order or two of data rate reduction.