Teens like Jake T experience issues, and some offenses like reckless driving and the likes. These pressures made him 'realize' that he is not fit for his roles. Odd right?
Before a wholesome country singer, now a free bird doing her own thing. This reason is very obvious.
Sharpey was too in demand and she had to choose well. If you're an ultimate fan, you'll understand that it's 'High School Musical' that gave her a very big break.
These brothers had a dream for the show, but when pitched, it was rejected. What's their choice? They left the set.
She's too old for the role. That's it!
Reasons that pushed her to retire were to look and try for more opportunities connected to her current career; and her crystal meth addiction.