Why/When do people paint their rooms different colours?

Ever since I owned my house, I have maintain the same Magnolia colour walls. Magnolia is fine for me, granted it doesn't set my heart alight. But it's pretty inoffensive. What do other people think of this colour?

Anyways, I was thinking to myself the other day that maybe I should explore a different colour. That's when I realised I have never even bothered to think about why/never had a reason to change colours. So out of interest....but also in search of some inspiration...I'd love to know why and when people do decide their room different colours?

Also - if you have any favourite colours. Fire away. I could do with an education!