One advantage of structured programming is reduced complexity. Modularity allows the programmer to tackle problems in logical fashion. Also, using logical structures ensures that the flow of control is clear.
Another advantage is an increase in productivity. Modularity allows multiple programmers to work on project at the same time. Modules can be re-used many times, which saves time and reduces complexity, but also increases reliability. It is also easier to update or fix the program by replacing individual modules rather than larger amounts of code.