My familiarity is more with Mandarin characters from simplified Chinese. However, I've noticed that there are certain characters that are used for colloquial spoken Cantonese that I just never see as much in Mandarin, including the following examples:
唔好意思 - Here the 唔 is used a lot for negation in Cantonese, but I see it far less in Mandarin.
冇問題 - Again, the 冇 here is used more frequently in Cantonese than I've seen for Mandarin.
你食咗飯未呀 - 咗 is another that looks to be used more in Cantonese.
My question is...is there some historical, cultural, or other reason for why these characters exist more in Cantonese? From what I gather, its similar to how chu nom from Vietnam adopted Chinese character for certain sound/meaning shifts.