I believe the reason why so much UI development takes place on the Web is because there are a lot more people making websites and web applications than there are making desktop applications. For example, think of all of the businesses and institutions, big and small, that need a web presence. Because the Web is such an essential part of modern commerce, it makes sense that there would be much more work available for web UI development than for desktop UI development. In addition, the Web is quite possibly one of the easiest platforms to deploy an application. Want to reach much of the world? Spin up a cloud VM, get yourself a static IP and a domain name, deploy your web server, and voila!
Another thing to consider is that native app development is fragmented. For one, there are a variety of platforms. There are four major commercial platforms for consumers: Windows, macOS, Android, and iOS. In addition, each platform has multiple ways of doing native development. I don't know much about the Android ecosystem, but in Windows you have a choice between (off the top of my head) Win32, MFC, WPF, and WinRT (and I may have forgotten a few), on the Mac you have a choice between AppKit and SwiftUI, and on iOS there's UIKit vs SwiftUI. Thus, it's not enough just to hire a developer based on platform; it's important to hire based on experience with the API your application uses.
In my opinion, my negative opinion of Electron on the desktop has nothing to do with laziness. There has always been a tradeoff between developer convenience and optimal performance in software engineering; for example, this is why I write machine learning code in Python instead of fine-tuned assembly. If that's lazy, I'm guilty as charged. Rather, my negative opinion is based on these issues:
1. A disregard for conforming to the platform's UI/UX guidelines, which are in place to ensure consistency in behavior across applications. By Webifying the desktop we get rid of one of the strongest advantages of desktop operating systems, which is consistency across applications, and we turn the desktop into the inconsistent hodgepodge of user interfaces that make up the Web.
2. Accessibility problems that are caused by ignoring the native platform's accessibility APIs.
3. Performance issues caused by running instances of entire web browsers to duplicate UI rendering features that already come with the UI toolkit of the system.
4. Applications written with the Web in mind for the desktop often inappropriately use design elements that may make sense in a web browser but do not make sense on a desktop (this is related to #1).
Some would say that #1 has long been the reality for Windows and Linux long before Electron existed due to competing toolkits (especially in the Linux desktop world) and app-centric viewpoints from application vendors where the look-and-feel of an app trumps platform consistency concerns for branding reasons. I agree. However, some say we should shrug, give up the dream of consistency, and accept having inconsistent applications. I believe there should be more consistency between applications (in fact, I disagree with the notion of app-centric desktop computing in general and strongly favor a component-style model, but that's another debate for another time), and I believe one of the strongest selling points of the Mac is the high degree of consistency that existed among the platform's applications for decades. The move toward Webified desktop apps undermine this consistency, however, and that I believe undermines one of the big things that make the Mac special.