Because from watching a few of various Sheik's pound videos, you were searching for very risky grabs and/or missing other chances simply because once the grab is landed, it leads to so much. Other players expected the grabs and punished according. Admittedly, a lot of the time it averaged out in the Sheik's favour, but safety is paramount at high levels. Miss a grab against Hbox and you can say goodbye to your stock.
Amsah seemed an exception, and he didn't put all his faith in the grab, and played far safer. Might just be bias because I was half expecting to see it, but I'm not sure.
TL;DR grabs aren't always the safest option, and safety is good at the highest levels of play.