It should also be noted that there is no technical reason why console player should not have access to mods. The only reason for is that the very idea of content for free is anathema to both $ony and M$.
They can increase the load on the system which has a very limited (at least by today's standards) amount of RAM, causing slow-downs and lock-ups.
Then there are those mods that require 3rd party executables to function, like SKSE (Skyrim Script Extender) and the like; these are programmed specifically for the PC and won't work on consoles (though, I suppose they could theoretically be ported if their developer had access to the console SDKs-At least the 360 SDK is free).
Even those mods that just change minor things DO increase the load on the hardware, even if it's only a tiny bit. If they allowed for an unlimited number of mods to be installed, eventually many players would be experiencing issues that they would not have otherwise ran into had they NOT been using mods. And we all know the average console gamer doesn't want to deal with these issues; that is one of the reasons why console gaming has become as big as it has: It's hassle free.
However, your second sentence does bring up an interesting point. Microsoft practically forces DLC to have a price tag associate with it. Valve mentioned this before in an email posted on their forums when talking about DLC for Portal 2. The content was free for PC players, but wasn't for 360 users because MS requires compensation for hosting the files on their service. PS3, however, has no such policy. There are PLENTY of games on PS3 that have totally free content packs, not to mention the PSN service itself is entirely free and actually offers much, much more than Xbox Live does.