This is my thought also, but not just because they wanted to offload the work, I think Beth got nervous about how far to take this whole marriage thing, as we've seen on the forums it get's plenty of snide comments, so Beth not wanting to risk upsetting some folk just threw in the basics, and man you could not get more basic!
If you can marry a lizard but can't marry a neko, your concept of "basic" is a bit wrong.
After all, people say http://knowyourmeme.com/memes/a-cat-is-fine-too, but I've never heard of people saying a lizard is fine too
Besides, come on, remove the ears and the silly garlic hairstyle (and give 'em French accent) and a Bosmer can pass as a Breton. Maybe they can pass khajiit as caravan traders and don't want to get married, but Bosmer?
Hell, depending on how you play the game, you can have a bosmer following you around Skyrim