Question

Why are the British and American spellings of some words different?

Answer 1

According to Wikipedia:

American English and British English (Commonwealth English) differ in several ways and among them are spelling differences. Many of the spelling differences come from a time when English spelling was not fully standardized. Some spellings seen as 'American' today were used in Britain, and vice-versa. An 'American standard' and a 'British standard' emerged in the 19th century, following the publishing of influential dictionaries.

Answer 2

My opinion ... because the Americans are lazy and they want to spell shorter and faster.