I'd like to add that in the US people rarely think of it as extra either. In most places in the US we also don't include taxes on the menu listed prices, but you know they will be on the final bill going in. The semantics of whether there should be tipping or not is hardly the line people should be arguing. What should be argued when discussing tipping is management abuses around tipping (like paying out others, stealing tips, or forced tip sharing), mandated minimum tipping, what items should be tipped and how much.

There is a ton of room to debate tipping culture in the US, but complaining about doing so isn't the right place.