When you think about working on a mainframe, the last thing you think about is pointing and clicking with a mouse. As a matter of fact, I remember when I first sat in front of a mainframe in college, the professor told us how lucky we were because we got to use COLOR terminals. There was no fancy interface like Windows, GNOME, KDE, or Aqua. A cursor and a keyboard was all you needed.
Fast forward 20 years and we discover that IBM is planning to spend about $100 million dollars in the next five years in an effort to deliver Mainframe Simplification. As a part of this effort, it's developing a new GUI interface to help what it calls the "new generation of IT workers" to do such things as manage, configure, and create applications for mainframe systems.
Entire cottage industries have popped up around the idea of creating graphical front ends for PCs to run mainframe applications. In those cases, the applications still runs on the mainframe itself but the presentation layer is all driven by the PC's horsepower. Consuming mainframe CPU cycles by actually pushing pixels around the screen seems like a rather surprising move.
When I worked on mainframes in college and at the Police Department, I had lots of discussions with the mainframe people about all of the benefits of smaller systems as opposed to the mainframe environment. Usability was always one of the issues. Running a GUI on something like a mainframe would have been completely anathema to their thought processes.
Now IBM comes along and brings the mainframe into the 1990s by creating a GUI for it. It very well may be one of the things that IBM has to do as the mainframe generation heads rapidly to the retirement home. IBM has already started investing in colleges to try and produce college graduates who are mainframe capable. Perhaps sinking $100 million dollars over the course of 5 years to bring 'modern' technology to the mainframe is a small price to pay.