Do I still need to provide real estate license, passbook and family photos to apply for a US visa? Why?

These are just supplementary materials, so you'd better take them with you when you get your visa, so that if the visa officer asks, you will have materials to show him. Sometimes the visa officer will ask, sometimes not. It's all personal luck

Generally, the purpose of preparing these materials is to prove that you still have a relationship with China, and you will definitely return to China after attending the activities. For example, you have a job now and a certificate from your work unit, which can prove that you still have a relationship with China. In addition, if you are married, and have wedding photos and family photos, to some extent, explain to the visa officer that you still have a home in China and will return to China after attending the activities. In addition, the passbook and real estate are all such proofs.

So it is generally best to bring this kind of thing. A friend of mine went to visit relatives, and the visa officer asked him for photos of his family. He didn't bring it, so the visa officer didn't give him a visa (he didn't refuse it), just told him to go home next time and get the photo to sign it, and then give him a visa after he brought it next time.