Why do companies buy your info?

Many Chinese companies have been found stealing info from their users, but what do they do with it? Depending on the site/app they will have a name, address, form of payment, email, etc. They sell this info to make money but why do companies buy it?? Online forums say it’s advertisements but there’s gotta be more to it if there’s so many companies gathering people’s info

address advertisements app chinese companies email etc forums info money name payment privacy sell stealing