"Will EK never learn?"
I don't usually get involved in these discussions but I think the main factors driving Emirates from taking up these "limited slots" are:
-Increased unit costs for less than daily service. When you open a station, there are certain costs associated that you have to pay regardless of whether you operate once a week or 7 times a week. Those costs are certainly higher on a unit basis when they are spread out over fewer flights.
-Either don't have the crews to layover there for up to 4 days or are unwilling to "lose" them for that amount of time. Again a cost vs. revenue thing.
While I think that in some areas, EK has sacrificed good judgement for lower costs, it's attention to details like this one that helps them run a profitable business. One thing that EK does very well is run the numbers commercially and it's my guess that they looked at Toronto/Cape Town with 4 flights weekly, the costs associated and potential revenue and decided they could make more money somewhere else.