Why doesn't the hair & make up designer have a single line credit under cast and crew details like other H.O.D's?

Why doesn't the hair & make up designer have a single line credit under cast and crew details of a production like other H.O.D's. Is this something that imdb could change? So the hair and make up designer has a single line credit above and the make-up department are listed below (as with the costume and art department for example)