I think the reason here is that Copilot is very very obviously inferior to Cursor, mostly because the model at its core is pretty dumb.
It's far more valuable to be a platform. Maybe Cursor can become a platform, but the race is on and they're up against giants that are moving rather surprisingly nimbly.
Github does way more, you can build on top of it, and they already have a metric ton of business relationships and enterprise customers.