I think numbering every line in a source-code editor is (very mildly) harmful. It adds visual clutter; and that’s a bad thing.
Often you need to find a particular line number, say to locate a failed assert() — but every programming editor has a “Go to line#” command, which is faster to use.
Showing the line number the cursor is on is worthwhile, because almost no display space is lost.
If you have your left-hand column set to show you line numbers, try turning it off and see what happens. You may be able to focus on your code ever so slightly better.