Why we need SOA?

SOA helps create greater alignment between IT and line of business while generating more flexibility - IT flexibility to support greater business flexibility. Your business processes are changing faster and faster and global competition requires the flexibility that SOA can provide.
  - SOA can help you get better reuse out of your existing IT investments as well as the new services you're developing today.
  - SOA makes integration of your IT investments easier by making use of well-defined interfaces between services.
  - SOA also provides an architectural model for integrating business partners’, customers’ and suppliers’ services into an enterprise’s business processes. This reduces cost and improves customer satisfaction.