It probably has a lot to do with psychology too. Consoles are generally used by richer people (children and adults) who, in addition to owning a computer, can afford to own consoles too (people who own consoles, in all likelihood, own computers before they own consoles).
These people are then less likely to be smiffed by a surcharge of a few dollars. Not that they like paying it, but they have fewer gripes. Companies, of course, home in on this very psyche.
The fact that consoles are closed also makes matters different, like so many before me have commented. But if the demographic it caters to failed, how would paid DLC ever have taken off?