So I know In-phase and Quadrature (IQ) data can be used to analyze changes in both phase and amplitude of the signal. I also know that if I know the I component of the signal (which I could get by measuring it with one oscillator), I could digitally get the Q component using Hilbert Transform. However, I know there are devices (like RTL-SDR sticks) that have two oscillators, 90 degrees out of phase of one another, so they can measure both the I and Q data analogically.
Why go through the trouble, engineering wise, of building such a device when one could always use a computer to generate the Q component by Hilbert transform from the I data? What is the advantage of measuring both?