Some students absolutely DO push their teachers to increase their grades! And then some parents email or call and push as well! Heck, they do that even when their kids are in undergrad
The ability to wheedle is a very important one, wherever you live in the world. Please develop it, it will stand you in good stead when you're negotiating salary or anything else. Personally, I'm not great at it. But one of my friends has a gift in that area. He's going to be charmingly pushy and get something extra, but without hurting feelings or offending anyone. I see him do it every week, but I can't replicate it!