Youjian App is a social interaction platform, which provides some special functions and services, and may require a certain fee to maintain the operation of the platform and provide a better user experience. Specifically, the reasons for charging 28 may involve the following aspects:

1. Professional services: Youjian App may provide services or consultation in some professional fields, which need the support of professionals or resources, so it needs to charge fees to pay related costs.

2. Advanced functions: Youjian App may provide some advanced functions or special functions, which may provide users with additional value and better experience, so it is necessary to charge for these functions.

3. Platform maintenance and operation expenses: The development and maintenance of a social platform involves server expenses, technical support, security and other costs. Charging can help the platform cover these expenses and ensure the normal operation of the platform.

it should be noted that the specific reasons for charging may be different due to factors such as platform policy, market demand and product positioning. If you have specific questions about charging 28 for Youjian App, I suggest you contact the customer service of the platform or refer to the relevant user agreement or terms of service for more detailed information.