Edit: The question title was changed. Previously, it was:
Why does Canada require mandatory bilingualism in all government posts?
Canada doesn't require bilingualism in all government posts.
Firstly, the federal government provides services in both official languages, but other levels of government don't necessarily. At the provincial level, Quebec is French and New Brunswick is bilingual, while all the other provinces are English, whether officially or not, but provide at least some services in French. For example Ontario has 26 designated areas where services must be available in French. Municipalities may also have their own language policies. For example the City of Ottawa is bilingual, in addition to being one of Ontario's designated bilingual areas.
Secondly, the federal government doesn't require bilingualism in all posts. Some jobs are unilingual English or unilingual French.
