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It's generally advisable for most users to always install the latest operating system updates, but there are legitimate reasons why some people would prefer to do them manually instead of having them forced on their systems automatically --- due to specific hardware configurations or legacy software that may break or cause conflicts, for example. In Windows 10 Home there's no official way to prevent updates, but people could workaround this by marking their Wi-Fi connection as metered.
Microsoft has slightly tweaked this in the latest Windows Insider build (15058) so that it can still push critical updates, even if you've marked your Wi-Fi connection as metered. The text under Settings > Update and Security > Windows Update specifically notes: "We'll automatically download and install updates, except on metered connections (where charges may apply). In that case, we'll automatically download only those updates required to keep Windows running smoothly."
Microsoft told WinSuperSite that it doesn't plan to send large updates over metered connections, but could use this for critical fixes if needed in the future. The Creators Update where this new policy is found is still pre-release software but given Microsoft's response it's unlikely this will change.
In a related charge coming with the Creators Update, the ability mark a wired connection as metered was added to the network connection settings as well.