We actually just merged it.
To re-iterate this; We didn't see a very good reason to change this, until now. 2.5 will have (partial) multi-threaded slicing, which can in some cases mean that 100% of your CPU is used if you are slicing. In that case it's kinda nice to be able to not slice all the time.
While we were at it, it also "remembers" if a re-slice is required. If this is the case, it removes the output button (Stream to wifi, usb, save to file, etc) and replaces it with a "prepare" button. Once it's completed, you get output button back again.
Note that you still need to disable the auto slicing in preferences before this works.
All that being said; We did listen, we just did not agree. There is a difference there. I've also had a people tell me that the slicing was faster when we simply hid the slicing progress.