I think there are few reasons about this.
If you have a bit age between you (ex. they 25 you 35) they wouldn't listen because of "neo-teenager-rebel-punk" bullshit, comes from their "youth-ego". Also if you are like same ages they wouldn't listen too because of "we are same age, why should i listen" bullshit.
As you say
useful for non-creative work that needs done (writing, putting together proposals, making simple tables, etc.).
They are not used to this kind of "creative" work. So try to different things as they used is can be a hard thing as you know.
I'm not a graphic designer but i work in a company too, so i can understand the problem. If you were my boss, i would like to talk with a coffee in a warm environment. But the main key is here is "respect". People tend to listen when they "respect" someone or something. If you can't make them to "respect" you, make them "respect" their job.