Yes.. i also believe that the competition can be an additional reason. There are alot of hosting servces around, even only in one country such as Croatia. And dropping prices seem to be the best way to beat the competition besides adding on quality and special services.
But it also seems that this availabilty of free server software was one of the main causes for the increasing number of hosts. When the price bars drop lower, many more people can jump in the business, be it reselling or starting from scratch.