Measuring skill in programming is much harder than measuring skill in chess. ELO is imperfect but you can be reasonably sure a 2100 will beat a 1200 most of the time. With programming, it's difficult to even make a choice between the person who write a sudoku solver in an afternoon or the person who makes a sturdy website which is secure against all known CVEs (but can't make a sudoku solver, or invert the proverbial binary tree on a whiteboard).