The tiller was used because the first cars were about as slow as boats, so they were steered with a tiller like boats. However as cars became faster and more powerful the tiller was no longer adequate, and thus the wheel was adopted as it simply worked better. Yet your example only proves the point: since the 19th century there has been NO CHANGE in this UI for steering a car. Once the wheel was invented, no one wanted to go back to the tiller and no one even invented some other way to steer a car. There is something optimal in the use of the steering wheel that makes any other refinements and changes useless.
Similarly the first graphic UI's were full of experimentation. Even the first Mac OS's had the menu bar in the window, but was moved out in early beta phase as the idea was that it was easier on the user to simply look always in the same place for the applications' commands, and has remained there ever since. Windows traditionally had the menu bar inside the window, with very little exceptions. However your example shows the same thing I am trying to get across: they DON'T change once they've made a decision.
X11 window managers actually gives you more choice - you can have either way or both. I think an argument can be made for either one. It seems that today, at least in Linux land, there is a tendancy to put the menu bar as something permanent on top (at least in Unity), but many desktops still keep the in-window menu bar.
To be honest I don't even like Mac OS X or Windows style menu bars. I actually use i3-wm as my hands are always on the keyboard. The mouse is a useless thing in my honest opinion, but for drawing and things like that it is indeed useful. Most of my work is at the keyboard, so I like the UI to be controllable with the keyboard. The menu bar is for some users needed, but I have different work habits from the era before we had X11 so I would say I'm more an exception than the rule.
In any case, my point stands: if it works for the user, don't change it. Every change involves an investment of time and energy which must be considered - is the amount of time to be gained by this new UI really worth the time it takes to learn it?