Child stars are funny critters. Once they start to grow pubic hair or develop a deeper voice, it generally means that Mickey Mouse can no longer work with the individual in question, usually tossing them to the pavement for Pluto to mock.
Once you've appeared in a Disney show, you somehow have to prove yourself so you can go on and get serious work.
There are a variety of ways to achieve this. Miley Cyrus posed in her undercrackers and had a go on a bong whilst Britney Spears and Christina Aguilera flashed their genitals. Vanessa Hudgens is known for being part of the irritating High School Musical franchise where everyone seemed worryingly happy on a permanent scale.