Since Laravel can auto resolve the dependencies, when should we need to create a service provider?

class Bar 
{
    ...
}

$app->get('/', function(Bar $bar) {
    dd($bar);
});

It works when I access the router / because Laravel can auto resolve the Bar::class and inject an instance of it .

I want to know since Laravel can do it automatically , then when should we need to create a service provider customly ?

Is there any case to show when to use service provider?