The last sealed tourney I went to, I beat the first guy I was putted against and he asked me to look at his deck. I helped him rebuilt it with the same colors, but quite a few different cards. I explained why we were choosing each change and why certain cards worked better together than others. He ended up 2-2 and largely, he said, because of what I helped him with. (Funnily enough, we played a for fun game afterwards and his revamped deck beat me, so he could have been 3-1.)
Helping newer players just makes the game better. It's not as fun to beat bad players, to me. So hopefully the guy learned something and next time we meet, he'll have built a better deck the first time, looking for the things I taught him. Then he's a better player, and a better challenge.