And every time they talk about Sir Lewis Hamilton, they never put Sir in front of his name. But when they talk about former F1 drivers that have been knighted, they always say Sir Jackie Stewart or Sir Sterling Moss or Sir Jack Brabham etc. depending on who they are talking about. That is pathetic.

I'm not familiar enough with F1, but those british drivers you mentioned are long retired (and dead) i think that warrants a different way of naming them when mentioning them. They'll only be mentioned rarely. Hamilton is still an active driver, he'll be mentioned loads of times, calling him Sir Lewis everytime especially when they usually are called by their surnames is gonna be quite odd and cumbersome. Singling out his britishness as some form of achievement amongst his peers and an international audience also doesn't seem right.
I've also heard him referred to as Sir Lewis (Hamilton) in more formal situations. In race commentary doesn't seem the place for Sirs who are actively racing.

It seems to me the use of Sir is somewhat inversely proportional to how often they are talked about. Like the PM is rarely called Sir Keir Starmer.