When Tridion user open a component, the component is checked out automatically, so it's impossible to open a component on 'read-only' especially non-shared item.

As a result, user modify content by mistake, or many components remain checked out (generally component is checked in when component is closed, but some times it remains checked out by unknow reason).

So following behaviour is preferable sometimes.

1. At first, component is not checked out when it opened,  it's read-only
2. When user click check out button, then the component is checked out.

This behaviour is not always better than current Tridion's behaviour (items is checked out automatically), so to allow users to choose which one they like, make it possible to configure which behaviour is used on configuration file or CME