The keystone of a well-designed network that can grow is a future-proofed IP addressing scheme.
Central to this are the two main tenets of Consistency and Hierarchy. These are vital to making your network coherent and orderly and assists in all manner of troubleshooting and planning issues.
It might be fine for your home network or small business to use a Class C (192.168.1.0) private addressing scheme for right now, and maybe for a while.
In the real world, this tends to be something that doesn’t get changed until it absolutely has to – at which point your network’s already grown to hundreds of devices. That’s large enough that changing the addressing scheme will always be a massive pain in the neck, taking hours upon hours of work and getting in everyone else’s way.
I’ve been a part of IP Addressing scheme changes in the past. It sucks. It takes forever, it’s tedious as hell for the poor saps who have to do it, and expensive for whoever foots the bill. And there is always bound to be things that go wrong and things you miss.
It’s always better to do things right the first time! So why not start with a scheme that can take you all the way from your small suburban office to an underground global headquarters where you torture British spies while patting a white fluffy cat.
Start it off right and you never have to make significant changes to it again.