They share the browser limited performance and bring a load of issues with them, they're at best a way to work around browser -> sensor access and bypass the appstores barrier.
For now, at least. The thing that will happen is that as they continue to "win", they find deeper ways into the platform. Cordova apps on Windows already run "first class" in the UWP app platform's JS stack. Electron apps don't currently, but there are bridges being built there too.
React Native and NativeScript are exploring different tactics beyond the most limited webviews on Android and iOS systems. Crosswalk and others explore yet another approach for bringing better webviews to such platforms.
At some point too, performance doesn't matter so long as the users are happy. A lot of technical folks notice performance, but most consumers do not. WebView-based application toolkits don't need performance to "win", they just need that sweet spot of developer productivity and user engagement that is much easier to do than you think, with or without "performance".
React Native and NativeScript are exploring different tactics beyond the most limited webviews on Android and iOS systems. Crosswalk and others explore yet another approach for bringing better webviews to such platforms.
At some point too, performance doesn't matter so long as the users are happy. A lot of technical folks notice performance, but most consumers do not. WebView-based application toolkits don't need performance to "win", they just need that sweet spot of developer productivity and user engagement that is much easier to do than you think, with or without "performance".