Landmarks app tutorial - need for UIKit

I was wondering if someone could explain or direct me to an explanation of why there's a need to work with UIKit late in the project (https://developer.apple.com/tutorials/swiftui/interfacing-with-uikit#introduction). What is it about that section of the tutorial that can't be accomplished using only SwiftUI?

I find the pre-SwiftUI Swift code to be extremely confusing and very repetitive–given that a lot of the code can be prefilled by Xcode (for example, when creating a UIViewControllerRepresentable, it will automatically insert a ton of protocol-stub code from the error/Fix window), so I'm also trying to figure out just what it is that SwiftUI can't do that Swift can. So if anyone has found a site or book that explains what SUI still can't handle, I'd love to hear back, as I haven't been able to find one myself.

Landmarks app tutorial - need for UIKit
 
 
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