Why we in China can't be a multi-cultural society rather than imposing the dominant Han culture on everyone?

Why not multi lingual? There are so many different Chinese dialects. Each province has its own distinct dialect. Thats for the spoken language. The written language is the same no matter what you speak. Mandarin was just chosen to standardize a language that everyone can learn. Everyone in China should be able to speak their native dialect and the main language putonghua or guo yu meaning regular language or country's language.