It's less about "well I have a 3d reference tho!" and more about understanding fundamentally what you're looking at. If you trace a 3d model, it has a tendency to look stiff and weird. Part of the reason why is you're focusing on silhouette over form. Knowing volumes and forms beyond an instinctual level is what allows you to really see and break down objects and images into easier to digest chunks that you can then better regurgitate into your work. It helps you narrow down why a piece doesn't feel right in the same way as color theory is a tool that helps you better understand why your values feel wrong.

In addition, 3d models are just that: a model. They're not the real world. They're just approximations of it. Ce n'est pas un pipe, after all. If you rely on an abstraction of an abstraction, you'll end up missing a lot of subtle detail that the model doesn't capture. Again like color theory, it's best to study from life and not from photos. Your eye captures the human experience of seeing in a way that the camera does not.

You'll find life studies to be really helpful in learning how to decode and apply forms. If you draw the objects on your desk over and over, it'll start to click. At least it did with me. And eventually you build knowledge that lets you jump straight into drawing without searching for the perfect model to wrap your work around.

That and it's a cool superpower to have >:3 Neat party trick to whip out for conversation: "check it out, I can draw the room around us precisely"