This isn't just true for web development thought. If you worked on building some piece of hardware, a few years later you'd be hard pressed to see any of that hardware still around. I guess you can keep one on your shelf as a memento, but it's not like it would work any better as a demo.
I did some hardware design for a product in my first job out of college 10 years ago. They are still shipping it. I'm sure they've updated the boards as parts go EOL (end of life), but they definitely didn't restart from scratch. I would like to get one, but it costs $30k+ [1]
