Microsoft 3D Viewer is a built-in app on Windows 10 designed to allow users to view, manipulate, and print 3D models. However, whether you need it depends on your specific needs and interests. Here are a few reasons why you might want to consider using Microsoft 3D Viewer.

1. Viewing 3D Models: If you work with 3D models frequently, Microsoft 3D Viewer can be a handy tool for viewing and inspecting various 3D file formats. It supports popular formats such as .obj, .stl, .ply, and .fbx, making it versatile for different types of 3D modeling projects.

2. Simple Editing Tools: While Microsoft 3D Viewer is not a full-blown 3D modeling software, it does offer basic editing tools for manipulating 3D models. These tools can be useful for making minor adjustments or annotations to your 3D designs.

3. 3D Printing Support: If you're into 3D printing, Microsoft 3D Viewer provides features for preparing and printing 3D models. It allows you to check the model's printability, set printing parameters, and send the model directly to a 3D printer.

4. Integration with Windows 10: Since Microsoft 3D Viewer is a native app on Windows 10, it seamlessly integrates with the operating system. This means you can easily open 3D models from File Explorer and directly access the app's features.

However, if your 3D modeling needs are more advanced and require extensive design capabilities, you may need to consider dedicated 3D modeling software such as Blender, Autodesk Fusion 360, or SolidWorks.

In conclusion, whether you need Microsoft 3D Viewer depends on your level of involvement with 3D modeling and printing. If you're a casual user or need a simple tool for viewing and basic editing of 3D models, Microsoft 3D Viewer can be a valuable addition to your toolkit. However, if you require more advanced 3D modeling features, you may want to explore other software options.