He is late. John is late right now. John be late. One recent example was the banning of indiginous Native American languages in schools, even in schools that were exclusively for Salish children for example. Even without political laws banning languages there can be considerable social pressure to conform to the majority dialect.
People can have trouble getting jobs, get poorer marks in school, etc.
Some countries go so far as to set up political bodies to regulate the use of language, such as the french academy. Occasionally political efforts are made to revive a language that has historical and national importance. Hebrew is the most successful example of this. Similar efforts have been made in Ireland, but with much less success. Some Black English Features Migration from other countries can cause new dialects of English to arise.