Why do some people say “warship” when they mean worship?

I never heard anybody say it that way.  Where are you, by the way?

Isn't it more the other way around? Most people pronounce War with more of an O sound than an A. Seriously. Try focusing on making an A sound with that word without sounding like you're from South Carolina.

ask them not us....

It's partly due to r-conditioning of the vowels, but that merger is very common in English. Linguists call it the horse-hoarse or north-force merger. There's an article on wikipedia, https://en.wikipedia.org/wiki/English-language_vowel_changes_before_historic_/r/#Horse%E2%80%93hoarse_merger

One is for atheists and the other is for Noah.