Why can't computers "be" a paper and pen?

Caution: Wearing one of my old hard-core techie hats today...

Previously, I wrote about the possibilities of using real-time multimedia communications over the Internet as a substitute for oil-based liquid fuels, with "substitute" used in the sense economists do.  That is, Internet communications can be a replacement for some types of current face-to-face communications enabled by cheap oil.  As part of that, I mentioned prototype software for such communication that I wrote almost 20 years ago.  This post is really just whining, but here it is anyway: why isn't real-time multimedia communications between people using the Internet easier?  In particular, why isn't it trivial for me to connect with a colleague and share high-quality paper-and-pen imagery?  Why can't I hold office hours for my calculus class here at home, with digital paper that's good enough to write derivatives and integrals as easily (and relatively densely) as I do on a white board?  Why can't the class be held online one or two days per week, with coordinated audio so that students can hear each other ask questions when called on, mark things up as necessary, hold side conversations without interrupting the other students, record what happens for later review?

There are some network reasons why things aren't as far along as I would like, based on how access to the Internet works in the US:

• For consumers, static IP addresses are the exception rather than the rule.  The baby router attached to my cable modem requests the same DHCP-assigned address it currently holds each day, but there are no guarantees that my ISP won't force me to take a new one.  There are ways around this, but it makes "I'll just give Mike a ring" harder to implement.
• ISP and backbone providers have been reluctant to implement IP multicast.  There are reasonable reasons for that, I suppose.  Multicast isn't essential for a multi-party call, but without it, some entity other than network routers has to be responsible for the necessary packet replication.  Pushing that out to the end client is a hassle because of...
• Asymmetric bandwidth configurations for most Internet access.  Client software on my Mac may be able to push video upstream to one other user; to push multiple copies of it upstream for a multi-party call is more difficult because of the bandwidth limits.
• Even disregarding the asymmetric bandwidth issue, setting up a "meet me" bridge on one of our home computers is probably at least a technical violation of the terms of service against operating a server.

That's not to say there aren't IP-based conferencing services.  One reason for my disappointment in the services that are offered -- and the large majority do seem to be for-pay services -- is my long-standing infatuation with paper and pen.  I want the "shared" part of the communication to do the things that are done with paper or paper substitutes that fit a particular situation.  For example, teachers and students meeting during office hours write on and point to a piece of paper that sits between them.  In a classroom, overhead slides and the whiteboard are larger versions of that, with more restricted access as to who can write when.  My version of collaboration starts with something one person has written or drawn, and everyone can debate and discuss and scribble all over it, like Arlo Guthrie's description in Alice's Restaurant, "...with circles and arrows and a paragraph on the back of each one..."  I'm simply not interested in sharing an animated PowerPoint presentation or many of the other "push" products and services that are out there.

Lastly, I want to bitch about the absence of any affordable IO device that can do a good approximation of paper and pen.  I suppose the problem is that I'm a mathematician at heart, and always will be.  And there's nothing as good as paper and pen for rapidly and clearly writing equations, sketching graphs, adding lines and boxes and annotations as needed.  Simple touch tablets like those made by Wacom and others separate the point of the pen from where the marks appear -- you can write with them, but not quickly and not in my tidy but cramped style.  Monitors that incorporate high-resolution touch tablet technology cost more than many computers.

All the things that computers do well... but none of them are an affordable substitute for a simple pad of paper and a pen.  Bummer.