I spent a lot of time trying to figure out how to automate the interface between my preferred password store (gnome-keyring, via libsecret), but with the loopback pinentry mode changes in gpg 2.1, it is much harder (if not impossible) to do. Having passphrase caching is the only thing preventing me from choosing a weaker passphrase on my gpg keyring.

Disallowing passphrase caching is likely to have the unintended consequence of users choosing weaker passphrases that are more easily memorized and/or typed. Caching should be permitted, IMO. This puts more decisions about passphrase management into the control of the user.