I spent two years preparing notes and delivering lectures 4-6x a week using a sketchpad.
1. If I put the pad on the right of the keyboard, then I can type normally, but I am writing at an awkward angle. If I put the pad right in front of me, then the keyboard is too far from me, and can't type fluidly. There is this continuous tension about where to place them.
2. Pads use bluetooth or wire to connect. If I use bluetooth, then my headphones must be wired. So there is a tradeoff there. Headphone are necessary for meetings.
3. There are the non-screen sketchpads, and the screen ones. The non-screen ones require a lot of hand-eye coordination (because you have to look at your monitor while drawing on the pad). They are not as stress-free as paper. The screen ones would help a lot more, but now you have two screens showing the same thing. The pad screen to draw things and move them around with your hand/pen, and the monitor to show you what you type. Kinda stupid.
Well, why not use just a ipad-like-tablet and both draw on it and type with a keyboard. Because drawing requires the surface to be flat, and keyboard require the screen to be verticalish so you can easily see what you are typing.
4. The software is still bad. There is still no native cross-platform sketchpad application with collaboration features built in, that will let me conduct a three hour online research meeting with dozens of pages of math. Browsers will inevitably crash, and are just slow.