Why does Answers.com spell certain words the English way?

Why not? There are several Englishes, and there are at least two standard Englishes: British English and US English. There are some differences in spelling and usage, but all in all not that many. Neither spelling of divergent words is incorrect.

Most differences between British and US English would be, I believe, in the more localized idioms or in casual language. When writing in the best standard or 'business' English of either variety, it would be very difficult to find language that would be confusing or misleading to reasonably well educated speakers of English.

However, for the sake of clarity and consistency, it is the official position of Answers.com's Q&A community that questions and answers be written in standard American (US) English.