Non-audio cables are commodities. When CHEAP is the goal, QUALITY suffers as anyone who've bought just about any cables for their computers knows. Most cheap cables need to be purchased many times from a variety of sources before you find a "good" one. And "good" in this context is the cable doesn't break within the first weeks. It doesn't take a Ph.D. to do the math and realize buying cables over and over isn't inexpensive.
Audio cables impact sound quality, so CHEAP is less important than QUALITY. Can you use the same cheap USB cables you use with your computer? Yes, but audiophiles and music lovers can do the math. They know cheap means loss of sonic detail, less musical magic. Is it a pain to organize audio cables so they don't become confused with every other cable threatening to overwhelm your life and tech?
Pain is a relative thing. Some won't care about sound quality. People who don't care about their music aren't likely to be here reading this. Neither the Roon Nucleus or Nucleus plus comes with any cables other than the power chord, so adding any DAC needs a USB cable.