First, the base model is $699, the pro is $999. Just to clear up as it sounds like you might have thought the $999 model was the base with USB2 speeds.

To answer your question shortly, it’s for the reasons above. You may not think you’re “a pro”, but moving hundreds of GBs of content by wire is absolutely a “pro” workflow. The more accurate term would be “prosumer”. Most people don’t do what you’re doing and don’t need to, therefore your use case would be better suited for professional hardware, rather than base model consumer hardware.

I fully expect the base model to get USB3 speeds over the next couple of years as usb-c on iPhones progresses. Apple does what a lot of manufacturers do, and bring their features from the previous flagship model to their lower end models over time. They also will often reuse parts in the base model from the previous year’s flagship. This is not exclusively an Apple thing. Strategically it’s a great way to funnel features and utilize premade hardware.

Other times Apple has done this:

• iPhone 5c (same internals as iPhone 5 with a bigger battery)

• all iPhone/ Apple Watch SE models (newer chipset in an older style enclosure)