LockerService is disabled for any component created before Summer ’17 because these components have an API version less than 40.0.
Component versioning enables you to associate a component with an API version. When you create a component, the default version is the latest API version. In Developer Console, click Bundle Version Settings in the right panel to set the component version.
For consistency and ease of debugging, we recommend that you set the same API version for all components in your app, when possible.