I guess the first type of cuts were made mostly to the 2013 version, at which time some of the quests may not even have been in production yet, or they are just poorly documented in the leaked files (e.g. "W3 ALPHA BUGS.xlsx" - this seems to be the most detailed for the quests it actually includes, but there is limited information in it about Act 3, and nothing about the Novigrad branch of Act 2). The story and quest structure in "W3 Quest Asset List.pdf" from June 2014 already looks more or less final, what was cut from that is probably for the second reason. Or possibly censorship in the case of Bald Mountain.
In case of Bald Mountain I kinda doubt the content was removed for censorship reasons. None of the animations for this section has been done by the time the most recent document came by. From what I recall they didn't remove just an orgy and ritualistic suicide, but also dancing around fire and throwing the items into it and I seriously doubt those turned out to be too hardcore (note how most of those animations were color coded red, which is used for a things cutted for scope cutting reasons). The most likely reason is the aforementioned scope cutting, since this section required a lot of unique animations and wasn't that crucial to the story, so when they started approaching deadline, all of that was completely dropped.
And to elaborate on first type of changes, most of them seem to be done in order to reduce the amount of "do something for me and I do something for you" in the main story. Here's example: in the initial concept of the game Crach would ask you to help Hjalmar first, before he gives you a permission to investigate cataclysm site. After you do so, you have to come back and then you find out that Cerys sailed to lift Udalryk's curse, so you have to help her, then you finally get permission from Crach. In the final game Crach gives you a permission right away and just ask you to help his children when you have a chance to do that, you can also decide who you wanna help first or at all. Turning those two main quests into the sidequests not only makes game structure less linear, but also make more sense for Crach's character (I mean he also obviously wants to help Ciri, so forcefully keeping Geralt and Yen like that from doing so would be a bit of a dick move). So as you can see, not every change from the original concept is for the worse.