Is adding ‘readonly’ to a DirectInjection service (in Symfony) useful? [duplicate]

In Symfony you can inject services into the controller and use them. I get the suggestion that the properties can be readonly. Please see the follow two examples:

class ExampleAController
{
    public function __construct(
        private FooService $fooService,
        private BarService $barService,
    ){}
}

class ExampleBController
{
    public function __construct(
        private readonly FooService $fooService,
        private readonly BarService $barService,
    ){}
}

Are there any realworld advantages/disadvantages to adding readonly here?

Adding readonly ensures it doesnt change and helps protect the code from unwanted changes, but in the case if a service, which often has its own dependencies, rewriting the property will be a lot or work and will not go unnoticed in any way.

To be clear, I’m specifically talking about services. If, for example, you inject a private readonly string $apiKey I can see somewhat of a benefit.