There is a change from Microsoft in the servicing model, going ahead from SQL 2017 there will No Service Packs.
Any vulnerabilities hotfixes will be roll out on need basis and issues will be addressed only through CU and GDR.
Going ahead we need to apply only CU to SQL Server to bring the system into servicing support cycle. J
More On: https://blogs.msdn.microsoft.com/sqlreleaseservices/announcing-the-modern-servicing-model-for-sql-server/