More cores so their phones can look more advanced to the specification sheet spotters, the mobile phone equivalent of train spotters.
My laptop only has two cores and seems to cope well. It is the speed of the core that is more important than how many of them you have. Given many multi-core chips tend to be clocked lower is seems fairly pointless.
If you want your device to be more responsible how about writing more of the code in C++ and stop using virtual machines with garbage collection (that tends to kick in at the wrong moment).