They've built tablets. We (developers) need to build the software that does more than consume our time, but allow us to create the content for others. Sadly, it's not there yet, but in time it will be. I don't doubt the computing capacity is there for a company to create a 3D modeling program for a tablet that's either touch driven, or a combo that includes a mouse and/or keyboard. There are already suites out there for image manipulation, music and video creation etc.
If I could purchase a tablet and then a full (3D) CAD or other modeling software for it, I'd drop the money in a heartbeat.