Another reason could also be that the servers operate in the same nation that you are from. If Apple or no suitable partner has servers in South Africa, that could also be a reason.
And, of course it could be politics. The South African government, I wouldn’t know, but it could be possible that they wouldn’t let tech companies from the US build servers in their nation.
Apple said it also will not offer "private relay" in Belarus, Colombia, Egypt, Kazakhstan, Saudi Arabia, South Africa, Turkmenistan, Uganda and the Philippines.
Some of them make sense to me, i.e. China which has a long history of censoring their citizens.
But in particular, I'm trying to find out why South Africa is on that list seeing as I live there.
Edit: In [1], Apple is quoted as saying, "We respect national laws wherever we operate" but did not elaborate further.
[1] https://mybroadband.co.za/news/internet/400893-apple-will-no...