Second of all, this is a convention issue, like tabs vs spaces, it could be one way, it could be the other way, in that sense I don't see how arguing that it could be the other way is helpful.
Either restaurant bills can be higher, or they can be a tad lower and tip is soft mandatory. It doesn't make much difference which way it is, the end result is the same. There's problems if you come from other conventions, in the same way that your device might burn if it comes from EU and you don't have a transformer.
Second of all, this is a convention issue, like tabs vs spaces, it could be one way, it could be the other way, in that sense I don't see how arguing that it could be the other way is helpful.
Either restaurant bills can be higher, or they can be a tad lower and tip is soft mandatory. It doesn't make much difference which way it is, the end result is the same. There's problems if you come from other conventions, in the same way that your device might burn if it comes from EU and you don't have a transformer.