Yes there was a good reason and it's the EXACT justification that Canonical and Microsoft are both ignoring with their development trends. Which is that Touchscreen hand-held computers (tablet, phone) and desktops have significantly different usage pattens, needs and expectations.
Trying to make the desktop interface operate like a tablet is frankly as stupid as making the hand-held interface require a keyboard and mouse. This is why most people hate Unity/Gnome3 and why Windows 8 is going to be a commercial disaster that makes Vista look like a raging success. These compute models are different animals and one size fits all is stupid, frankly given the trend I'm startled Google was smart enough to see this from the start, and they saw it years before both the current companies proved it doesn't work.
Don't get me wrong, there can be similarities and compatability (Canonical has been moving slowly this direction) but to throw out the usage paradigm of desktops and replace it with gestures and touchscreen paradigms is a recipe for being lynched by the users.