[ecuzzillo]

Pieces of software basically never exist in a vacuum; they're always connected to other pieces of software and hardware (compilers, processors, graphics cards, phones, OSs, libraries, web services, ...). Other pieces of software and hardware always change, and if there's no one home improving this particular piece of software, it will invariably lose pieces of functionality, one by one, as they change to be incompatible with how they were before or disappear entirely because they lost to a competitor or turned out to be a bad idea.

Users know this instinctively, which is why a website that never changes loses users quickly.