Simple as that. Many games are won or lost on one or two points and a free throw can make all the difference.
It's 'free' (my favourite price). No one is defending you and you have a whole 10 seconds to shoot.
Being able to do it well is a huge asset and means that you can play more aggressively. If you shoot and are fouled then it's a chance for more points.
The video below shows you everything you need to know to improve your percentage at the line.
Click on the resources below to take you to some more information on how to manage and structure your practice and for specific ideas for drills and skills.