Why Do We Need A Reason To Learn?

Why is it that so many of us only attempt to learn new things either for school or a job? Why don't we take the time out of our lives to learn something new for no reason, simply because we think it will be fun? What has brought this topic to my attention and inspired me to write this blog post is the fact that I am currently taking a Spanish class for school, and so far am thoroughly enjoying it. Since I am enrolled in this class, I obviously have an incentive to learn as much Spanish as I can in order to do my best in the class. But why is this?
I've always wanted to learn a second language, and I have attempted to learn Spanish in the past, but I never really gave it a good attempt. Even though it was something that interested me and that I thought would be really fun to learn, I didn't stick with it. I think the reason for this was because I really didn't have a purpose to learn it. But now that I do need to learn Spanish, I am reviewing and doing homework every day in order to soak up as much as possible in preparation for my Spanish class.
So I guess this all leads me to my ultimate question: why do we need a reason to learn something new? Many of us (myself included) do try and learn something new based on the fact that we think it's fun, but typically we give up and stop trying. Only when we have a reason for learning it, whether it be to pass a class, complete a task at work, or because someone else is telling us to go do it that we keep up with learning something new. So, I will end with this: go learn something new because YOU want to, and make yourself the incentive to learn it!