Build tools simplify the process of creating modern web frameworks like React and Angular by bundling dynamic JavaScript code into statically-bundled content, making it more approachable for developers. They automate the process of building programs through Make-like automation, providing scriptable ways to enhance bundles into smaller modules for lazy loading and optimizations. Build tools have evolved from old concepts like scripting and build automation, and are now used to package websites with features like minification and module bundling, making it easier to maintain and deploy static assets. They abstract client databases or sensitive information, improving security and scalability. With the rise of JavaScript fatigue, new build tools are emerging, such as Gulp and webpack, which have strong communities and can manage large JavaScript applications into manageable static content.