Originally posted by froze
Also it's easier to fix the front tire. Now one tire company has recognized this problem and has made a pair of tires to be sold only in pairs where the rear tire is slighty larger with thicker tread and dual kevlar belts whereas the front is lighter, narrower with a thinner tread and only one kevlar belt. That company is Continental new Attack/Force tires advertised in Coloradocyclist. Why would a leading tire manufacture do this?
The front tire is easier to fix than the rear? I assume what you're actually suggesting is that some folks find it more difficult to remove and re-install the rear wheel since they need to deal with the rear derailleur and chain. Practice or instruction can reduce this difficulty factor to about a 3 second difference in repair time -- otherwise there is no other difference in replacing or patching a tube.
As for recognizing the "problem" Continental has taken a page out of the Shimano play book and created a solution looking for a problem that doesn't exist. As to why they would do this? Well, isn't it obvious - you even answered your own question when you noted that you'd rather buy them one at a time. Continental wants to sell more tires.
Sorry to sound to cynical, but these are bicycle tires we're talking about. The only mystery is figuring out why they cost as much as they do and why road bike tires even have tread pattens since it serves absolutely no useful purpose.