Why the ESC key removed from Intellipoint 5.x button assignments?

This one has me baffled.

Intellipoint 4.x software used to allow the user to assign the ESC key to
mouse buttons. Intellipoint 5.x software does not allow this. Why?

I've grown so used to having one of my buttons assigned to ESC for AutoCAD,
I can't operate without it. So far, I'm still using the 4.12 drivers with no
major issues, but if that should change, I see no alternative but to dump all
my Microsoft mice/trackballs and switch to another brand.

I know that this is an old topic but I found it in a google search so I thought I'd add a few lines to help anyone searching for a work-around to this issue.

I don't know why MS decided to remove the Esc key but I've found a 'work-around' because I too need it for AutoCAD...

1. Choose "Macro Editor..." from the drop list under the desired button
2. Click the [ New ] button to create a new macro
3. Give the Macro a name (I called it "Esc")
4. Now click the [ Insert Special... ] button and select "Esc" from the drop list
5. Click the [ Save ] button
6. Click the [ OK ] button
7. Now you will be taken back to the Mouse properties screen where you can select your new macro (Macro...(Esc)) from the drop list under the desired button.
8. Click [ OK ] to confirm the macro
9. Click [ OK ] again ...and all should be set up