ICAO allows for intersection departures. However local state/county regulations or as ICAO refers to them (local ATS Authorities) may impose restrictions there-upon. Reasons for intersection departures are redundant to ATC's as the PIC is ultimately responsible for safety of aircraft and passengers.
In ref to SA ATC's being busier per controller than those in the USA or Europe, somewhat of a naive perspective. SA ATC's have an extremely high standard to which they operate and do indeed work a high level of traffic, but compared to many cetres in the USA, even at county level, they are rather tame when it comes to any one number of aircraft on any frequency at any given time.
The same applies to Europe and most of the Middle East.