No interface, the nipple included, is intuitive to 100% of people. When we talk about an interface being intuitive, we mean that it is intuitive for someone.

Mac programs feel intuitive to Mac users. Windows programs feel intuitive to Windows users. Any kind of software is more intuitive to those who have experience with computers than to those who don't.

When designing an interface, you need to know your users and make your interface intuitive to them.