Inertia lazy shared data

Hi guys,

can someone explain me how does lazy shared data work in inertia?

https://inertiajs.com/shared-data

class HandleInertiaRequests extends Middleware
{
    public function share(Request $request)
    {
        return array_merge(parent::share($request), [
            // Synchronously...
            'appName' => config('app.name'),

            // Lazily...
            'auth.user' => fn () => $request->user()
                ? $request->user()->only('id', 'name', 'email')
                : null,
        ]);
    }
}

If I tried it, the data still was in every response.