This would be a small usability improvement. Right now, when you add a REST export display, you immediately get an error saying a path hasn't been specified. You then need to manually specify a path, and it's not clear as an end user a) where that is, and b) what you'd put in there. The flow is kind of like this:
Suggestion would be that if the View already has a Page display (such as the Frontpage view), just carry over that path so the user never gets this error in the first place. This would mirror how entities work (what you get on node/1 depends on what headers you sent). And in my testing, if you specify /node as the REST export path of the Frontage view, and shoot text/html you get back HTML, if you shoot application/json+hal, you get back JSON, so it seems to work as expected.