But to be fair though the rest are not all streaming their own event on their own platform.
For those who had to squint and think for a second, Microsoft owns Mixer (formerly known as Beam) https://en.wikipedia.org/wiki/Mixer_(service)
Microsoft also has Microsoft Stream which I understand is more for Microsoft 365/Office 365 customers
> Microsoft Stream is a corporate video-sharing service which was released on June 20, 2017 that will gradually replace the existing Office 365 Video.
Microsoft Stream is basically login-required corporate YouTube, and as you surmised wouldn't really fit this model.
[1] https://azure.microsoft.com/en-us/services/media-services/