I find that the syntax highlighting clutters the interface so much that I can't tell if I have accurately highlighted the content that I want to copy. As such, it results in me frequently copying and pasting the entire line by accident. I would rather copy *nothing* than copy an entire line of code.
If I want the entire line of code, I can always triple-click the line to select it and then copy it. So the need to copy a line when there's no selection is redundant anyway and the "convenience" results in UX failures.