Hello and welcome to Advanced Installer forums,
This most probably happens because you are adding SQL Server (actually, any other prerequisite will behave the same) as a "Feature-Based" prerequisite.
Please keep in mind that, for feature-based and post-install prerequisites, on below Enterprise project types
only the "Full UI" install command line can be used and the prerequisite will be installed only if the main package is run with full UI. All other command line fields will be ignored and the prerequisite will not be installed if the main package is installed with silent or basic UI.
More details can be found in our
"Prerequisite Setup Files Tab" article.
With SQL Server 2014 LocalDB, everything works fine.
This probably happens because you have added "SQL Server 2014 LocalDB" as a pre-install prerequisite instead of feature-based prerequisite.
Please let me know if there is anything else I could help you with.
Best regards,
Catalin