When you are connected to the Internet through a network with limited bandwidth or restricted data plan it is desirable to reduce the data consumption. In this case, disabling iCloud sync is something you want to do.
In Windows, you can easily mark a wifi network as limited by data plan and this will automatically inhibit Windows updates to download and it will also make cloud services not to sync.
In the world of Apple and Mac OSX, it seems like Apple assumes that when you are on a wireless or wired network, bandwidth is unlimited. Period. If this only was true, what a great world to live in! The news is that this is not how it works in the real world. Unfortunaly, because of this there is no function to disable or pause iCloud syncing at all. A simple feature present in all other cloud services like One-drive, Dropbox etc.
The solution, which works excellent is called TripMode. This piece of software gives you the control you want over any application using your Internet data.