I stand to be corrected but I think the British consular birth certificate has a point in one circumstance - if the British parent(s) of a child born outside Britain is/are themselves born abroad, they are not "patrials" and as such their child does not acquire British citizenship unless the birth is registered with the Consulate.
This point is worth keeping in mind if your spouse is/was not British at birth and you have children who are British - your grandchildren may lose British citizenship if born abroad and unregistered.
