Maybe Google can by traversing the virtual DOM and other trickery but it's not as simple for other small players. Moreover, in a healthy web I should be able to easily deeplink to something I'm thinking about without jumping through hoops. The SPA web is not as easily discoverable and connected as it is very much meant to be. I think there are valid arguments to be made for SPA, like that SPA need to SPA because they are not just a series of pages and documents but complex applications which need to be that way (though I would still tread with caution: I remember java applets and javascript bits doing complex things, submerged within pages, and that was all fine).