[quote=@The Grey Warden]
<Snipped quote by The Nexerus>

You could also reacquired sovereignty over South Africa...
[/quote]

South Africa doesn't have the same cultural connectivity to the United Kingdom that Canada, Australia and New Zealand do. There's also no 'big bad' for South Africa, whereas with Canada there is the United States, and with Australia and New Zealand there is the East Asian blob.

This isn't about maximizing the power or extent of the UK, it's about what makes the most sense.