The members area is designed to keep your business information safe. Each time you log in, you create a "session" and get a number that identifies you. That number is good for 7 days from the last time you logged in. If you log out, you destroy that number.

Why is this a good idea??

Most browsers keep a copy of web pages you have visited inside your computer. if someone wanted to change your account, they could access those pages on your computer and change your account information. If you log out, the code on those pages will become invalid and not allow access to your account.