I can't speak for braindrop, though I'd guess it's the patreon risk, but for me it isn't about the amount of work. Whether I'm working on scene A or scene B, I'm having fun. It's more about a balance between choice and content. Every choice means less content per playthrough.
Take the christmas supper for example. I had to make about 40% extra dialogue and renders because Tanya is optional. Now imagine if everyone there was optional. There would have to be dozens of alternate versions for it and it would take 2-3 updates just to get through that supper. And then the Cat/Liz threesome, I would have to make a Liz, a Cat and a threesome scene. 150 renders x 3 scenes = 450, that's about 75% of an update just for a single scene.
Also it seems like the large majority of players don't have a problem with the main 7 so I would be taking away a ton of content from them so a handful of people could avoid someone. It just doesn't make sense to me from either a hobby/passion project or job/business point of view. If I wanted to make the 7 optional, I would have to pretty much cut out all the other LIs. And I'm pretty sure I would have a fucking riot on my hands if I killed off the O'Reilly's
To be fair to braindrop though, let's be real here, how many of us would risk 250k a year just to give people on the internet some incest porn