Failing to plan is planning to fail.
When organizations first begin implementing Azure networking, the focus is often on the immediate requirements: connectivity, security, and performance for your databases and applications. While that is important, the reality is that your environment will change at some point in the future. Developers will deploy new resources, more users will connect, hybrid scenarios will evolve, and security needs will continue to grow and adapt. If you only plan for today, you risk painting yourself into a corner tomorrow.