Many people type with Cangjie because that's what gets taught. Very few people know Jyutping, and even fewer type with it; most people encountering Jyutping for the first time wouldn't know how to pronounce it, largely because of the unfamiliar 'j' and 'eo'.

For day to day transliterations of names etc there's actually no standard, just some loose rules based on English pronunciation.

In HK, pronounciation of Cantonese words is usually just learnt orally without much formal Romanization. You wouldn't encounter Jyutping unless you're a linguist studying the language, or you study it as a non-native speaker. Similarly, a native English speaker most likely didn't learn English words by using e.g. the International Phonetic alphabet.

As an aside this has caused colloquial Cantonese prounciation to "shift" over the years [0], it's called "lazy tone". E.g. 你 (you), the proper way is 'nei5', but most younger people say it 'lei5'. It's a big debate whether this trend ought to be stopped or not.

[0] https://en.wikipedia.org/wiki/Proper_Cantonese_pronunciation

Most people use either Cangjie or the number pad on their phones. Office communications are generally conducted in English but where Chinese is needed, Cangjie is the preferred method. Our keyboards all have both QWERTY and 手田水口廿卜 printed on them.