TBF Stephen Lawrence's murder was shocking because he was apparently chosen at random just because of his skin colour, while all those others you mention were either personal disputes or gang warfare.
I think a closer comparison is the murder of Kriss Donald, who, like Stephen Lawrence, was picked because he was a "white boy from the McCulloch Street area" despite having no involvement in any gang activity.
https://en.wikipedia.org/wiki/Murder_of_Kriss_Donald
That said, your point stands, because yes, it's strange that everyone still knows about Stephen Lawrence, but nobody seems to care much about poor Kriss Donald.