Why do Hong Kong people always write traditional Chinese characters? Can't they write simplified Chinese characters?

Before the founding of New China, traditional Chinese characters were used all over the country. Because handwriting is difficult, what's worse, there are many illiterates. In many ancient dramas, there will be a profession of "writing letters from home", but now there is no such profession, because most people can write. After the founding of New China, ZF simplified Chinese characters so that everyone could read. Also changed to a more vernacular writing. Hong Kong and Taiwan Province Province have not changed due to historical reasons. After the return of Hong Kong, "one country, two systems" will remain unchanged for 50 years. Hong Kong is located in Guangdong Province, which was under the jurisdiction of Guangdong before it was occupied by Britain.