Why do people use concealer like lipstick/gloss?

some of my friends and other girls i know put concealer on their lips.. sometimes theyll put like colourless gloss on over it but why would you want to make it look like you have no lips? i'd understand if you put colour over it like pink or something so the colour is clearer, but just leaving it nude? it looks awful. these people are mainly the more chavvy if that has anything to do with it? i've seen it while walking around other towns and other cities as well.