When developing a trial site (before it goes live), it’s usually necessary to configure the system domain (trial site domain) for the correct ‘Start Page’, ‘Currency and Format’ and ‘Country’ - especially for eCommerce sites.
When it’s time to go live with the site and you add your custom domain, its domain settings are initially set to system defaults so you need to configure the new domain the same as your trial domain.
However, it’s very easy to overlook this and forget to correctly set the new domain since it doesn’t really happen in the same step as adding the domain (usually caught up in DNS settings, etc.), and this often leads to problems occurring after going live, like; product prices disappearing, incorrect price formatting or taxes applied, incorrect language settings, etc.
It would be great if any newly added domain would simply copy the configuration of the system domain, by default, to eliminate these problems and make going live one step easier.