"credit system" is far less established than countries like US, and private companies are generally much less trusted by the government and by the people (which is the opposite to the US). Some big private companies like Alibaba has started to create credit systems themselves, but the state owned banks and law enforcement would only use something backed by the government.
The "social credit system" it actually not that different from other credit systems excepted it is managed by government. It's really needed now given that there was a rising debt default problem -> Without a credit system, many people thought they can just delete the app where they borrowed money and get away with it. It became a crisis when a lot of this happened at the same time.
Surveillance is a separate topic. It's one of the technology advances that made law enforcement easier (like DNA samples are much more used nowadays in identifying criminals). There has been reports that criminals being captured with these new tools. It's something that western people fears a lot, so all the western reports focuses on the negative side of it and exaggerate it many times more.