One of the Visual Dictionaries mentions that the traditional Jedi robes are similar to those worn by common people across the galaxy. On Tatooine, look no further than Uncle Owen's robes.
But such modest attire is unusual on Coruscant (home of military uniforms, ludicrous senatorial getups, etc.), and I imagine this is why during the prequel era they tended to stand out in the crowd. Not to mention with Jedi frequently out and about and seen on news broadcasts, folks like the waitress droid would be more likely to recognize Jedi robes.
While it seems most Jedi favor some variation on the bathrobes, the colors and styles vary, and some even opt for flightsuits or Aayla-type catsuits.