The short version is that laypeople with a skeptical bent like to say "eh I don't believe in dark matter, those silly physicists are inventing particles that aren't there, MOND solves the problem without extra particles so MOND is probably right."

It's an easy way to be "skeptical" without really knowing anything about the relative success of the two theories. Because MOND is an underdog theory, you can feel like a skeptic questioning dogma by supporting it... even if you don't really know much about the merits.