Edit: Sorry for wall of text.
I have spoken to some creators of BE visual novels and many of them say its just so much work to account for every change in a character portrait when you make a decision for one person to have BE while another doesn't. you have to account for all the dialogue paths and update your code to be aware of multiple instances where the portraits may be different.
If this is the outlook of developers who make 2d art and shy away from BE due to the extra work it may account for:
To this I say, you can cut a lot of the headache out by making the options locked in, or linear. what I mean is give the player a path to choose near the beginning that goes linear, any future branching paths will be set, but you do not need to retroactively go back to past parts of the story to account for changes if that size is never shown earlier.
So many times in a game (like a japanese VN) do they have a BE sequence but its only temporary, or as an epilogue, and I think its because they see it as too much work. I also think that's why so many japanese devs still use RPG maker because its easier to program for different portrait sizes with the framework.
An example of what I mean. Here's a game in the VNDB That says this game has BE in it, but its only for one scene and then goes away afterwards.
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I think many creators get a bit too ambitious with their stories, and never having cut their teeth on smaller projects before, they get overwhelmed, and tap out early, or try to find an easier way to do it. then that usually involves all the old stuff being scrapped.
For example: you could have a story where you commit to a heroine early on and are stuck with that path. any future branching path would be to make them bigger or stay the same.
Another could be you want multiple heroines at the same time to grow, now that path is locked in.
However if you do a path where you pick one, grow them, then decide to change your focus to someone else in a BE story, you add a moving part that becomes harder and harder to account for, the more you progress in development. I tip my hat to the cabin by the lake dev because he's made a ton of moving parts that require going back and making checks for all levels of corruption. But if you find it unrealistic because of this, you have to know there are ways to make the experience simpler with BE.