Strangely Microsoft's one is missing: Application Insights.
Pretty much works like Google Analytics but utilises both client JavaScript and embedded runtime code to generate a richer picture of what is going on.
Too bad the interface on the Azure Portal is terrible. They spent too much time making it look fancy, and not enough time getting the 101s of usability right (which is a criticism I'd lay at the feed of the new Azure portal in general).
Probably the vendors of the software concerned. Perhaps it started out as a list of three with a major bias towards a particular product. And then the competitors responded, moderators did their things and eventually an accurate list was evolved.