Sir / Ma'am

Im am legally working here in china, and I want my family to visit me here, I gave all the requirements they need from me like passport copy and my visa copy, and also the requirements they need to gave to embassy, like passport photo and proof of relationship to me. she filled up the form and checked the visiting relative for purpose to travel. why the embassy ask they need also have a show money too. at least 50 thousand minimum in a bank. why? it is a new policy to all new applicants?