Adding those kinks from the beginning would have made no sense as D was very sexually repressed in Chapter 1. Its a thing called character progression. The story has shown her journey from naïve virgin to sexual being.
Chapter 1: Getting D over her sexual hang ups.
Chapter 2: Become a couple and enjoying more sex.
Chapter 3: Introduction to swinging and sex with others.
Chapter 4: Further exploring the different options with sex.
And no, people don't have to skip them just to get to those kinks. That assumes they don't also enjoy the non sharing sex too when they easily can. And, as has been pointed out many times, this content hasn't been hidden, they have been planned from the 1st Chapter. The MMF path starts in Chapter 1, though, it does take until Chapter 3 for anything to actually happen. Swinging is also introduced in Chapter 1 with the Olivia scenes as it is clear Olivia is also dating her father. The whole point of the petals around her portrait was also to show her corruption level and she gets more and more kinky.
Chapter 1: Getting D over her sexual hang ups.
Chapter 2: Become a couple and enjoying more sex.
Chapter 3: Introduction to swinging and sex with others.
Chapter 4: Further exploring the different options with sex.
And no, people don't have to skip them just to get to those kinks. That assumes they don't also enjoy the non sharing sex too when they easily can. And, as has been pointed out many times, this content hasn't been hidden, they have been planned from the 1st Chapter. The MMF path starts in Chapter 1, though, it does take until Chapter 3 for anything to actually happen. Swinging is also introduced in Chapter 1 with the Olivia scenes as it is clear Olivia is also dating her father. The whole point of the petals around her portrait was also to show her corruption level and she gets more and more kinky.