one reason they would be reluctant to do this is that it would

And you don't think people are already furious?

In my opinion, Microsoft is making a simple thing very complicated by making
it very mysterious.   The principal that one license should appear on one
machine is easy for any honest person to accept.   The way to enforce
licenses is to give honest people the tools they need to enforce the
license.   If I buy a retail product and activate it on my computer, then
find out two weeks later that someone else is trying to grab my product key
and use it to activate their computer, I would surely forbid the transfer.
The problems are that:

1) Microsoft gives us no way to know that someone else is stealing our
licenses.

2) Microsoft punishes the buyer for the theft by forcing the buyer to make
phone calls to manually activate his own license (again).

3) Microsoft tries to make up for all of these duplicate activations by
producing products with ever smaller numbers of activations.   It's just
ridiculous and unfair.

The way I would like it to work is that I have unlimited activations for the
software, and I can transfer it between machines unlimited numbers of times.
BUT, the license is registered on Microsoft's servers, and activating a
license on any machine requires me to explicitly cancel the previous
activation.    That in turn should send an e-mail to the originally
registered owner asking for confirmation that it is okay to cancel that old
license.

A scheme like the above allows the user to self-manage his own license
without resorting to draconian schemes.   And very importantly it gives the
original licensee perfect insight into whether someone else is trying to use
his product key.   The original licensee could forbid transfers to any new
machine, thus largely protecting Microsoft (and the user) from stolen
activations.

The above scheme also protects the licensee from innocent mistakes within
the same company, where the product key may have inadvertently been used on
two machines.

Instead Microsoft is resorting to the most anti-consumer and completely
unfair restrictions on numbers of activations, numbers of transfers, etc.
All of this forces people to buy the software two or three times for one
computer if they have enough hardware expansions or failures, which is
completely unfair and just maddening.  And very importantly: these kinds of
draconian measures do NOT build consumer loyalty towards licensing
provisions.   Microsoft will never win against piracy unless it can recruit
the consumer to act on its behalf.   That requires fairness and empowerment,
and the current situation has very little of either.