New and Improved Mac App
Although Apple offers a Mac version of its Messages app, it’s lagged pretty far behind what the iOS apps are capable of, having not really received any major updates since iOS 10 began delivering new effects, handwriting, and stickers. macOS High Sierra gained the ability to make reactions and at least recognize the new iOS 10 features, but otherwise the Messages app on Mac has plodded along as a second-class citizen to its iOS brethren.
Thanks to Apple’s Project Catalyst, however, it looks like Apple will be able to bring a much more full-featured version of iMessage to the Mac, and there’s already been evidence found in macOS Catalina that it’s on the way. Since many of the new features Apple is testing for iMessage right now will need to come to the Mac, it probably makes more sense to unify the iOS and macOS app than release an update to the existing Mac app that’s already behind the times.