In real life I only rarely use lipliners. The only time I find them necessary is when I am determined to wear non-permanent lipstick, with lipliners protecting the already fragile color from escaping and my shaky hand from crossing the boundaries of true lips.

I recently realized that many girls are negligent when wearing only gloss on their lips, because they smear it on recklessly, not really paying attention to lip contours. On a bright, sunshiny day, you can see gloss all over their lips, and some also on the outer side. Looks bad, clumsy and not at all attractive.

So, if you're a sheer gloss lover, you might consider investing in Cargo Reverse Lipliner:

The Reverse Lipliner was created for lipgloss lovers everywhere. This unique, natural colored Pencil adds definition and fullness to the lip line, as it locks color in place. No more feathering! Can also be used in the inner lower eyelid to brighten the eye.