I see nothing but benefit having an internal metronome. Why not? Are we running out of room? Those wanting to haul around / insert / apply an external click can always do so. All-in-one capacity is much appreciated; in this case, especially when practicing alone with headphones.
Not specifically in regards to a metronome, but as someone who works as a developer for his day job I can tell you that everything you say "yes" to including has a cost. And when I say it has a cost I mean beyond the obvious one for the man hours that go into making even something as seemingly simple as a metronome.
I don't mean to pick on you exactly, I just see a lot of posts in the feature request section that write in the same way, as if there's no cost to including their feature. There is, even if it doesn't seem obvious to you!
A few examples, off the top of my head:
* Expanding the user interface to include controls for the feature, possibly complicating life for users not interested in that feature
* Supporting the feature after it has been developed (bug fixes, having to support a larger code base going forward, with more possibility for error and more code to rewrite when improving code)
* Stability. Even a metronome on the Kemper probably needs extensive testing, this device has to be rock solid always, no exceptions
Saying "no" in software development is super hard. We always want to give our clients and users everything they ask for! But it is also one of the most important things.