How do you make your network scalable?

I'm studying for my CCNA and came across this aspect of a network: scalability. Now, I understand that the network should be scalable (obviously, and especially, for enterprise networks). But, isn't this aspect already implemented when you purchase modern networking equipment? Like, isn't scalability already included in the up-to-date models of the equipment?

What would a network engineer have to do to ensure a network is scalable, apart from purchasing updated equipment when the network is initially installed?

I may not be in the right spot, so forgive me.