Especially European languages. It doesn't even need to be a thing that supports multiple languages within the same cart. I would be willing to pay for separate carts for every language I want to sell in.
And no need to complete multilanguage support, either. Just giving access to text, so that users can enter the terms in the language of their choice, would work.
Users who browse in their native language (and fall on a native language site) don't expect to find an English cart and click buttons and fill in terms they don't understand. Which means, 1SC becomes a barrier for any natively non-English site.
Royal Campus commented
Yes, multilingual support is a critical success factor in Europe and South America, especially the languages German, Spain and French.