Why do people get labor epidurals since it causes so many back problems later in life?

Very low risk. I have to disagree with you--epidurals very rarely cause any long-term problems, and often are used in the treatment of back pain from other causes. Labor epidurals are the safest way to manage labors which are severely painful, and can also be extended to provide anesthesia if a c-section is necessary. They very seldom cause any back pain other than temporary soreness at the insertion site.