Undo's (and especially re-do) are quite hard and resource intensive to code, especially for web apps that can be simultaneously accessed via multiple devices.
E.g. you can take action A on your laptop, followed by action B on your phone. Undoing action A may not be easily possible if it was followed by action B.
To make that work properly you need to activel sync states between all the users devices using e.g. websocket or what-have-you. Handling edge cases becomes quite the nightmare, e.g. phone has poor connectivity.
Only the big guys would have budget to do these sort of things (And make them work well).
