I think your parent is arguing that, despite TaskCompletionSource exists, some people still don't use it much and resort to callbacks (presumably because they h

I think your parent is arguing that, despite TaskCompletionSource exists, some people still don't use it much and resort to callbacks (presumably because they have not learned about it). As in “adding TaskCompletionSource to the framework didn't help some folks adjusting to Task style, and they keep using callbacks”.