It is a British v. American thing. As with many common spelling differences across the Pond (like -or v. -our, and -er v. -re ), the US spelling is the origina

It is a British v. American thing. As with many common spelling differences across the Pond (like -or v. -our, and -er v. -re ), the US spelling is the original, and the current British spelling is a later Francophile affectation, from a conveniently forgotten time long ago (18-19th C), when the British admired and copied French culture. It is usually computer program in British English due to US influence on modern British spelling in areas of technology, perhaps perpetuated by the tendency of hackers to prefer terse names. You continue to see TV programme and concert programme in British English. As in many things, the British prefer the principle of pragmatic de facto bottom-up evolution, based on common sense and common usage. So the OED was famously compiled by collecting fragments of real language use. Language pedants in Britain are usually ridiculed, in a similar way to those who fancy themselves as public intellectuals. Compare this with the French tendency towards dictatorial de jure top-down control, as shown by the Académie Française's specification of correct French. The rest of Europe is similar, see Royal Spanish Academy, Council for German Orthography, ... https://en.wikipedia.org/wiki/List_of_language_regulators https://en.wikipedia.org/wiki/List_of_language_regulators France also has a thriving industry of respected public intellectuals. Another example is the British Common Law system based on precedents in case law, compared to strict prescriptive Napoleonic Codes. Britain has no written constitution and no National Day - the Queen's Birthday is celebrated, but it's not a public holiday. Even the name and boundaries are fluid, as the full abbreviation UKGB&NI attests.