It must be a daunting chore to maintain all the legacy pages. The amount of now-years-old stuff that long-standing sites have to maintain, or choose to maintain, is shockingly high, and testing the combination of all that stuff is impossible.
If you want an example of how diverse in age these apps are, dig around in the Gmail settings panel. Eventually you will land on a popup that uses the original Gmail look and feel, from 2004.
If you want an example of how diverse in age these apps are, dig around in the Gmail settings panel. Eventually you will land on a popup that uses the original Gmail look and feel, from 2004.