Touch and mouse are two very distinct forms of input that need to be kept separate. Every convertible Windows laptop I have ever used has convinced me of that.

Mouse interfaces can be incredibly information dense because mice are both incredibly economic from a space and motion standpoint, and also somehow incredibly precise. You can flick your wrist to select any target the size of a grain of rice on a 32" screen. Touch interfaces require larger targets because fingertips are larger than a cursor point, and also require smaller screens because your arm now has to move the entire length of the screen, which is slow and tiring.

Where touchscreens excel is tactile experiences, things that mice cannot replicate. Multi-touch, pressure sensitivity, pen angle. Sweeping motions are difficult to control with a mouse. Manipulating multiple analog controls is nigh-impossible with a mouse.

When an app tries to accommodate both input styles, it inevitably ends up catering to one style or the other, unless two separate interfaces are built. And because a touchscreen laptop can be touched or have the mouse moved at any given time, it's not really possible to switch between the two input styles seamlessly.

I would really enjoy having a device that is capable of both, since the iPad has a gorgeous screen, a great form factor, and a lot of killer uses. But it can't cannibalize mouse interfaces or we wind up with the direction that MacOS is going.

There is nothing wrong with having a keyboard connected to a touch device per se, but the gross arm motion required to move between the touchscreen and the keyboard, and the awkward angle the keyboard puts the touchscreen at sort of nukes the usefulness of the touchscreen. And again, jumping in text is the sort of small target action that mice excel at.