Why not? In English we don't all use the same words for the same objects or concepts.
True... but it's probably very close to 95% and getting closer. I mean okay there are differences, but trade-wise, it's almost entirely the same. For instance, if you're in the store, and you want to buy bread, you can ask someone where the bread is. It doesn't matter whether you're in the US or UK or Australia or even in some countries in Asia, you can go "Where's the bread?" and people will understand it. Or worse comes to worst you can still say "Bread?" and someone might point you in the right direction.
Or with a really heavy accent, you could even say "buredo".. like a lot of Japanese do, and people would still get it.
But if you approach a signer in a store in a foreign country, and you sign "bread where" you might as well not be signing for all the difference it will make.
Am I right when I say the sign for "bread" is different in pretty much every country? I'm not talking about say, complicated concepts like antidisestablishmentarianism. I'm talking about stuff like bread and water. Stuff that you sort of need to survive, that you have to know otherwise you'd just starve to death or spend an hour wandering around the store
I mean, if you're not in a total backwater country, you'd at least be able to find someone that speaks English, even if it's not very well. So you could fly to the UK or Australia next month, and people would more or less understand you, you'd be able to find a hotel, find food, transport etc.
Why don't people at least agree on the basic terms? :P
The other thing is that, because of that, it has no history or tradition. I'm reading Eliot's Middlemarch right now, it was written 139 years ago. Through her I can see what things used to be like. But 139 years ago, what was it like to be deaf? no one knows. No records exist from back then.