I would strongly argue against the no creativity in realism thing. By that argument, photographers have no creativity because they 'just take pictures of what they see'. How you interpret these things becomes your creativity. You can still do 'realism' with a strong voice shining through. I know of realism oil painters who have wonderful mood and drama in their paintings. Yes, some artists replicate and create visually and emotionally dead images, but if you are a quote unquote good painter or creator with something charging you to paint, your tendencies, vision and voice naturally effect how you see. That usually becomes style. Not even all realistic painters work looks the same. Why? Not all photographer's work looks the same, why?
I think the reason we as artists need to be creative, is to express something we can't otherwise. That is what usually motivates us to start making stuff in the first place. Even if you look at very strict traditional painters of old, you can see the translation of real world to the canvas. Whether you are creating something based on your own concept or painting a very realistic commission where you soften someone's face or brighten their eye to flatter them, you are being creative to a certain extent (in my strong opinion).
There is also the question of what creativity is. It's definitely not exclusive to artists. Engineers, doctors, and scientists are creative. To me, creativity rests in creating solutions or solving problems, and making stuff. 'Stuff' can be a suspension bridge, a medical treatment, a scientific discovery based on years of experiments, a new way to plan cities, or a painting. To create is to cause something to come into being. And to me, to also solve a problem. Is the problem a need for automatically dispensing food from machines? Is the problem expressing your personal story? Is the problem putting into words ideas and feelings that are universal? Is the problem a logo for a mom & pop shop? I dunno.
Creativity is important because it brings into the world new things. New needed things. Would we have cars, schools, movies, the internet, or even cutlery if someone hadn't seen the need to bring something into being that wasn't there?
It's hard for me to see how an artist wouldn't need to be creative. Yes some things are similar to what has been previously done. Yes some things don't require the most innovative, new, or flashy solution. But if you are making something, then you are being creative.
At least, that's my opinion :)