Based on the information you have provided, here are three possible reasons why project management team members might use PrimaViewer to view Primavera P6 files:

1. Cost-effective solution: PrimaViewer is a relatively affordable option for teams that need to access Primavera P6 files but don’t require the full suite of features that come with a more expensive project management software package. At $595 per year for 5 users, PrimaViewer is an affordable way to view and collaborate on project schedules.

2. Web-based convenience: PrimaViewer is a web-based tool, which means that users can access it from anywhere with an internet connection. This makes it easy for team members who are working remotely or who are on-the-go to stay connected to the project schedule.

3. User-friendly interface: PrimaViewer is designed to be user-friendly and easy to use, which means that even team members who are not familiar with Primavera P6 or project management software, in general, can quickly learn how to navigate the tool. This can help to reduce the amount of time and resources required for training and support.