Honestly, Robin can work in a movie. People, fans and writers alike, just cling to the idea that if they use Robin "everyone will think he's gay with Batman" or he takes away from Batman's "seriousness". They're excuses at the end of the day.
I doubt we'd ever see it, but I'd love to see a Batman franchise that embraces the Batfamily at large, giving us Batman, Robin, Nightwing, Oracle (or Babs as Batgirl), and others. The comics themselves even drive home the point that for all his talk and reputation as a "brooding loner", Batman actually has a close knit team of people he considers family.