This is like making a car where the airbags only deploy if you hit another car of the same brand. Sure, if this car is super safe it may be better if both you

This is like making a car where the airbags only deploy if you hit another car of the same brand. Sure, if this car is super safe it may be better if both you and the other driver both had it. But it is clearly better to have airbags, even if the other car is less safe than it could be if it was from the first-party brand. It is one thing to not try to mitigate security issues outside their control and another thing to remove possible security because you don't control it entirely.