Why configure L7 monitor in GTM for PCF applications load-balancing

I came across a GTM-LTM-GoRouter setup, where a common set of GoRouters are the pool-members for all the LTM VIPs and are monitored with TCP (L4) monitor. Whereas, GTMs which are configured with the FQDNs of the various applications have the VIPs of these LTMs as pool-members. However, as a monitor a HTTPS (L7) monitor is deployed. I am not sure why we have this kind of setup. Is it something needed for the PCF kind of deployment?