People are conditioned to pretend to agree and to pretend to care. Much of school is about teaching students to pretend to listen or pretend to agree. When someone asks "How are you?" usually they are pretending to care.

It can be annoying when someone pretends to want do something to instead of being honest, but it can also be annoying for to the event planner to plan an event only for no one to want to participate.

When the people around you are routinely dishonest(in subtle ways), as is common in school, work or society, it feels necessary to adapt the same behavior to conform to the norm.