Why top touring bikes have no suspension forks?
There are a couple of reasons.

The KISS Principle

If anything vital breaks while you're touring and you can't fix it on the spot, you're stranded. You're too far from home to call your mom for a ride. Unless you have a spare for the broken part, your options are some DIY jerry rigging and/or praying that someone with a truck comes by who will carry you and all your stuff to the nearest town. There's less that can go wrong with a rigid fork, so less chance of being stranded. 

Standard parts are easier to replace and repair

Rack-ready suspension forks are irreplaceable, irrepairable abominations. Ok, that's an exaggeration. But it's definitely harder to get a replacement or get it repaired. Head shock? Only one of the three bike shops in my town sells Cannondale stuff. If you end up in a smaller town with one bike shop (or none) you may be out of luck. If you find yourself limping along to some no-name town in the middle of nowhere, your best hope for repairs is to have standard parts. 

It's true that you can find mounting apparatuses (apparatii?) that will allow a rack to mount to a standard suspension fork but they all require additional parts, violating the KISS Principle.

Weight

In spite of (or perhaps, because of) the abundance of gear that tourists carry, there are weight-weenie tourists. Suspension forks are heavy. Or at least heavier. 

Efficiency

Another reason is that a suspension absorbs energy, and rationing ones energy is a primary concern of the long-distance tourist. 

Physics (supposedly)

When I first got into touring there was a notion that suspension forks weren't designed to withstand the lateral forces of braking well enough to add weight to the fork. The idea was that the forward force of the bike's weight on the steer tube and the forward weight of the panniers on the lowers would flex the fork and damage it. This seems to have either been overcome or disproven, but old ideas sometimes die hard. This is probably the reason that Giant used such a bizarre contraption on the front of their Expedition AT, to compensate for those forces.

Most people just don't need it

Most people tour on the road where suspension doesn't really do enough to justify all the other costs. 

As others have mentioned in the comments, if you're having wrist pains there is most likely a fit/setup issue with your bike. There are any number of possible solutions, all of which would be specific to you and your bike. See your LBS for advice.