Mods add content for free, which equals less money for MS/Sony not Bethesda, because everyone who can buy the game for the PC will buy it for the PC, which equals most of the target audience. Bethesda also is irrelevant in this case, MS/Sony are the driving force behind not allowing ANY mods. They don't not allow it just because they're simply cruel as well, because you CAN break your game/savegames through modding. I myself had to deactivate 3 mods today, because they caused random crashes even though they didn't edit anything in the area my character was in.
Mods would also be restricted by the hardware. You wouldn't get most graphical enhancement mods as well as some other (Wars in Skyrim and Warzones off the top of my head) , because consoles simply can't handle most of them (which is the reason why the texture pack DLC is PC only).
Now I don't see any reason, why Bethesda shouldn't add some of the most popular mods via patches, but they can't offer much free DLC on the consoles (MS/Sony want provisions for allowing them) and therefore no control for the players as to what mods they would want to install. Charging money for player created content on the consoles would certainly cause an outcry in the modding community and Beth certainly doesn't want that, because THAT would definitely equal less sales for them.
As for the command console. It would need to be heavily restricted as well, because spawning 50000 cheese rolls can cause your game to crash and you can be sure, that somewhere, someone would be stupid enough to do this on a console!
On the command console issue specifically, yes it could and practically guaranteed would freeze your game. So what? You can turn off the console, and turn it back on. Can commands make a save completely unplayable? Yes, and it would happen to some. However, that would be the individual player's fault, not Bethesda's or MS's or Sony's fault. If the individual screws up their game save, they can load from another save or start a new game if they were foolish enough to not have backup saves. Also as mentioned, you can also manually fix or get workarounds to some bugs with the command console.
For instance, I froze my Gamecube many many times using the Action Replay disc for SSBM, which granted you access to the actual game's developer debug menu, when I spawned too many items. I've used a Gameshark on a Pokemon save I had, and somehow it ended up entirely deleting an NPC (just one of the ferry ladies) from that game save. Do I blame Nintendo, Game Freak, AR, etc? Not at all. It was purely my own fault for those, and if I had messed up a game save, I had backups.

I believe the technical aspect has little or nothing to do with the command console not being in. I'm not sure what the issue is myself, though someone mentioned cheating to get achievments, which sounds much more likely a reason to me.
On a smaller note, I thought there was a bug or something where spawning more than 500 of any item at once would freeze the game no matter what anyway.