I think one of the big reasons for creating a new interface was that the XO's screen is really small -- it's about as wide as 1.5 times the largest dimension of an iPhone. While its resolution is roughly the same as a standard desktop, its pixels-per-inch is 2-3 times as high.
This places screen real-estate at a premium... Essentially all applications will be running maximized, so title bars and other window decorations are a waste of space, as is having a menu/launching bar at the top or bottom of the screen.
And due to the XO's high pixels-per-inch, all text needs to be roughly 2-3 times larger in pixels than on a traditional display. Many applications on existing systems do not cope well with this requirement; most of the X11 applications that have been minimally ported to Sugar have text that is illegibly small.
The device's display is closer to a hand-held device than a typical laptop, so OLPC decided it needs a different UI than a typical laptop. And OLPC is not the only organization to make this choice: There are a number of manufacturers who are releasing Android-powered netbooks in the near future, as opposed to using more traditional UIs.
Unfortunately, Android was not an option at the time the XO was being developed. I imagine Maemo or Qtopia were not chosen for either licensing or maturity concerns. Any of these options would probably have been an OK alternative to Sugar, but none of them is a traditional overlapping-windows interface.
This places screen real-estate at a premium... Essentially all applications will be running maximized, so title bars and other window decorations are a waste of space, as is having a menu/launching bar at the top or bottom of the screen.
And due to the XO's high pixels-per-inch, all text needs to be roughly 2-3 times larger in pixels than on a traditional display. Many applications on existing systems do not cope well with this requirement; most of the X11 applications that have been minimally ported to Sugar have text that is illegibly small.
The device's display is closer to a hand-held device than a typical laptop, so OLPC decided it needs a different UI than a typical laptop. And OLPC is not the only organization to make this choice: There are a number of manufacturers who are releasing Android-powered netbooks in the near future, as opposed to using more traditional UIs.
Unfortunately, Android was not an option at the time the XO was being developed. I imagine Maemo or Qtopia were not chosen for either licensing or maturity concerns. Any of these options would probably have been an OK alternative to Sugar, but none of them is a traditional overlapping-windows interface.