Back to the top buttons are a symptom of the system-within-a-system feature of Web. The Web page isn't a document: it's a system, a virtual machine. Just like running another OS in VirtualBox implies bad interoperability and a lot of duplicated effort with the host OS, so too does running web pages. In a quest to be everything, Web became a bogged down, developer-time devouring beast. It can do almost anything, but you don't want to do anything on it.
It means universal, think smalltalk. Has ups and downs - not much integration with a host comes with independence from a host. IE was created because Microsoft feared web would make OS inconsiderable. There was bold claim even before Netscape's Constellation [1]. So everything goes like it was predicted years ago.
