This is a weird thing to tie to graphic designers. Just because you noticed a graphic designer doing that doesn't mean it's a thing that's more commonly practiced among graphic designers than any other trade.
The reason is most people can tell red from green and big from small, and most people use graphic designs daily, so will have an opinion on whether a design element should be bigger or redder.
Other professionals with a similar plight could be copywriters, and devs when selling a PR.
Compare to plumbers or lawyers.