Why "systemctl" is not honouring Drop-Ins ( /etc/systemd/system/name.type.d/*.conf ) ?

Issue

• Why "systemctl enable" command is not creating symlink if "WantedBy" parameter mentioned in "/etc/systemd/system/name.type.d/.conf"* ?
• Why systemd unit file configuration is not overwritten by "/etc/systemd/system/name.type.d/.conf"* ?
• Why parameters in "Install" Section of a Drop-In file is not being reflected in "systemctl enable" command ?
• "add-wants" and "add-requires" feature in "systemctl" command for RHEL 7