Why do some people not tan?

There are a few reasons why some people do not tan. One reason is that they have very little melanin in their skin to begin with. Melanin is the pigment that gives your skin its colour, and people with less of it will generally not tan as easily or as deeply as those with more melanin. Using tanning lotion can improve your tan.  You can also speak to tanning salon staff members about increasing the duration of time you spend on the sunbed, in line with your skin type.