DLCs are made to milk money from an existing game, not to add much content to it.
Compare how much content you buy with the game itself and how much content in playtime an DLC offers.
The game is the printer, the DLC the ink.
DLCs are done on a smaller budget than that of the main game, which is one of the other major factors, and yes, they also serve to make extra money off the base game, which is the cynical way to look at it.
I can't find it anywhere Bethesda stating that Marriage goes against Khajiit and Bosmer's culture, way too many people are saying that they both don't believe in the Nine-divines as the others do, but I keep looking at the lore and it says they both have members of the Nine-divines in their Pantheon >:|
Where is the source of Bethesda responding to this problem people have been having?
It was supposedly stated in a dev diary somewhere, but I'm not certain as to where. It's something that other people have claimed that Bethesda had said. It may have been mentioned in a special feature they released for the collector's edition they did, since I can't find it on their website.
Still, I think it would be rather blasphemous if they justify not doing Khajiit and Bosmer marriage options because of so-called "lore reasons," while on the flip side of things they completely go against all lore of vampires by making them all carbon copies of Oblivion's variety of vampires, and very likely go against all established lore to make every werewolf in the entirety of Tamriel
Spoiler identical to the Companions variety of werewolves, as well as continuing to completely retcon the lore on the Night Mother in every single game. Seriously, the lore of the Night Mother is so completely and thoroughly inconsistent that it makes the Star Wars prequel trilogy look completely consistent with the original versions of the Original Trilogy, if you could even believe that.
It would be nice if they could at least somewhat follow the lore or stick with stuff they write for once, and at least give a very good explanation as to why certain things weren't implemented as they should, and in certain cases, actually consider doing something about it in DLC. I don't mind a little retcon here and there if it's meant to clear up parts of the lore that were rather muddy or a little sub par (such as the Alduin/Akatosh thing), but I don't like unnecessary retcons where they shouldn't exist (like trying to pass off werebears as a mythical thing that doesn't exist or the possibility that they retconned marriage out of the lore for Bosmer and Khajiit).