It gives you the ability to treat nulls as something-to-fix.
In a team without Optionals, every time you touch a null that you didn't expect, you have to decide "Is this deliberately null, or was it a mistake?" Without that knowledge, you don't know whether your code should assert against the null, or allow it to pass through as a valid value.
With Optionals, it becomes much simpler to cut through that nonsense. A null is a bug and you fix it (with the exception of json at the boundaries of your system, etc.) If you do find a value where you change your mind about its nullability, changing it to/from Optional will give you compile errors in exactly those other parts of the code that you now have to check/change.
In a team without Optionals, every time you touch a null that you didn't expect, you have to decide "Is this deliberately null, or was it a mistake?" Without that knowledge, you don't know whether your code should assert against the null, or allow it to pass through as a valid value.
With Optionals, it becomes much simpler to cut through that nonsense. A null is a bug and you fix it (with the exception of json at the boundaries of your system, etc.) If you do find a value where you change your mind about its nullability, changing it to/from Optional will give you compile errors in exactly those other parts of the code that you now have to check/change.