Does the rear tyre carry more weight than the front tyre?
Generally, the weight distribution of a rider on a bicycle is something like 40 - 60 rather than 50-50 (front to back). This contributes to increased rear tire wear (along with rear wheel drive) causing front tires to sometimes last three times as long as rear tires. Skid stops (such as on a fixie) can also increase rear tire wear relative to normal stops.

An aside: You don't need to run your tires at equal pressure - in fact, in most cases, the rear tire is about 10% higher than the front tire. This will make it deflect a bit less.