Perhaps the best motivation for going to Mars is political. It is obvious that no single nation currently has either the will or the resources to do it alone but a consortium of nations and space agencies could achieve it within 20 years.
I wanted to be a great white hunter a prospector for gold or a slave trader. But then when I was eight my parents sent me to a boarding school in South Africa. It was the equivalent of a British public school with cold showers beatings and rotten food. But what it also had was a library full of books.