Why do mobile phones always receive IP SMS and MMS?

When you surf the Internet with your mobile phone, some websites will record your browsing traces, and send you something you might like according to your browsing content and your hobbies. These things may be free. If they are free, the website is to improve people's popularity, but he will often send you similar short messages in the future, and it may be charged, but there are usually tips for charging, whether it is charged or free, as long as you ignore him.