A change to the status quo can be very threatening if there's the possibility of a considerable downside. The problem is that such frustrations eventually leak out. Even the most empathetic partner may interpret the signs of frustration as rejection or loss of attractiveness. It's easy to take something like this personally. The frustrated person may find it easier to blame the other, as well.
Some people are surprise junkies.
They love the unknown, even in their sexuality. Most people seek ways to reduce senseless risk in sexual adventures yet still find ways to feed their desire for the exotic, unknown, and surprising. Some people are willing to go home with a stranger they met at a bar and try kinky sex with them. For these people, the element of surprise is essential. They crave an edge of fear to feel vibrantly alive.