I see that different clients implemented in different languages will need different client-libraries and maintaining all that is not something, a core project is going to do but if using the raw protocol instead of the convenience of libsystemd is a (commonly ignored) recommendation which makes a lot of sense in terms of segmentation, providing at least one reference implementation would point all systemd users into the right direction.
Recommending that each client should just implement the (trivial) protocol access itself does not make so much sense to me.