Domains and hosting are usually seen very differently. Your domain is a lot closer to property, while the hosting is commonly shut down anytime it is seen as inconvenient by the provider.
If you combine them on the same provider you risk loosing access to the former because you lost the latter, the providers that host all the services also tend to have blurred lines between disabling one service and disabling your whole account.
If you combine them on the same provider you risk loosing access to the former because you lost the latter, the providers that host all the services also tend to have blurred lines between disabling one service and disabling your whole account.