The CAA or any regulatory body will regulate to cover their own backs as well as the obvious safety angle.
I have been flying for 35 years nowadays totally CAS but going back knew many airfields where unpublished procedures were used by even professional pilots usually with a lot of local knowledge and usually on an NDM or other aid with a GPS overlay
A bad pilot can mess up and crash on a published procedure the published part doesn't mean an unpublished procedure isnt cannot itself be a good procedure only that it is not published i.e approved
I am not at all promoting the use of un published procedures but stating the fact that throughout that course of 35 years I know of many even used by professional pilots
OCAS it was probably considered as "creative flying" for those who must fly rather than choose to