As a matter of fact this is all primarily a historical problem.
I suppose that the TN-C system was sort of trick to introduce a grounding in an existing ungrounded pre-war two wire installation at a time when RCD were merely ideas, as first working and payable RCDs were developped in the 60's.
And properly done, with a majority of devices with metal bodies or frames it was a lot safer than before.
Nevertheless, in Germany TN-C up to the level of an appartment or house main switch panel is still quite normal for everything that is more than 20 years old. And on the level of PoCo it is probably the majority.
